alt.contour reactivated

* Introduce rdoxygen2 commands in the R functions for easier and cleaner contruction of the documentation.
*
* Include the possibility to plot results from the ICON model.
* Replaced fixed variable names like HSURF and FR\_LAND by their CF standard\_name.

* Introduce rdoxygen2 commands in the R functions for easier and cleaner contruction of the documentation.
*
* Include the possibility to plot results from the ICON model.
* Replaced fixed variable names like HSURF and FR\_LAND by their CF standard\_name.

correct error in plotmap.R in case option levs are given but cols not

correct bug in plotting flag_values and flag_meanings<br>
affected modules:

* plotmap.R
* plot_colourbar.R

correct bug for plotting the right triangle in plot_colourbar.R

Corect typo in file DESCRIPTION

Removed: *plot_colourbar.R*, *plotmap.old.R*

Replaced: *ncdf_times.R* by *nccf_times.R*

In **colfun.R**

* Fixed errors in *get.ethz.palette* and  *get.ncar.palette*

In **plot_colourbar.R**

* new option *sea.lab* , *border*, *triangle_ends*

In **plotmap.R**

* new options *sea.lab* and *lakes*, changed option name *scale_factor* to *scale.factor*

In **polymask.R**

* added support for multiple polygons

In **windvec.R**

* added new option *legend.scale*

-------------------------

**Changed functions:**

`plotmap`

* Has been rewritten in large parts. It should work now not just for geographical and rotated model coordinates, by for most structured grids, if additional geographic lat/lon data are provided for the model grid.
* An additional small model area can no longer be plotted. For this plot a rectangle of the small model area over the plot or use the old version `plotmap.old`

*New Options*

* units - default=NULL (overwrites the units from the netCDF file)
* longname - default=NULL (overwrites the longname from the netCDF file)
* add.offset - default=0
* scale.factor - default=1
* geo.coordinate.names - default=c("lon,"lat") 2D fields of the geographical longitude and latitude at the model grid points

*Removed Options*

* file.small
* sponge.small
* lsm.file.small

**New functions:**

`windvec`

* plots wind vectors over a given plot

`geo2mod`

* converts geographical coordinates to model coordinates

`get.ethz.palette`

* gets a palette from the web page https://wiki.c2sm.ethz.ch/Data/VisNCLCosmoLibraryColorTables

`get.ncar.palette`

* gets a palette from the web page http://www.ncl.ucar.edu/Document/Graphics/color_table_gallery.shtml

**Depecreated functions:**

The old version of the function `plotmap` is now called `plotmap.old`. This function will stay as is and will not be further developped.

-------------------------

*Changed functions:*

@plotmap.R@ -- corrected bug in case of grid.txt=T,
               eliminated artificial straight lines across the plot showing up under some circumstances
               eliminated errors plotting grid and writing grid labels in some cases when the date line
               or/and a pole lies in the plotting area

*New functions:*

@plotmask.R@ -- creates a mask file from a given polygon

@plotmap.R@ -- Introduced new paramenter "pollonshift" to account for pollat=90, pollon=180 (TRUE, default)
               and pollat=90, pollon=0 (FALSE) representing rotated == geographical grid

@geo2rot.R@ —- Introduced new paramenter "pollonshift" to account for pollat=90, pollon=180 (TRUE, default)
               and pollat=90, pollon=0 (FALSE) representing rotated == geographical grid.
               Corrected error in case pollat=90, pollon /= 0., pollonshift=FALSE

-------------------------

*Changed functions:*

@ncdf_times.R@ -- changed default time from CET to UTC
                  changed input format of reference time to %Y-%m-%d %H:%M:%

@plot_colourbar.R@ -- changed label "sea" to "water".
                      Direction of the axis description now depends on which side the
                      axis is plotted.

@plotmap.R@ -- grid labels can be set on and of for each axis separately.
               New parameter grid.lwd for the line width of the grid.
               Missing reading of attribute earth_radius for multiple_rotated_pole transformation added.
               Distinguish for 3D variables whether the third dimension is time or level

-------------------------

*Removed functions:*
@nc_open.R@ -- is no longer necessary since ncdf4 package (version >= 1.6.1) considers
             _FillValue as attribute holding missing values

@plotmap_rot.R@ -- the new plotmap.R function includes rotated coordinates

*Changed functions:*
@geo2rot.R@ -- calculates the special case pollat=90.,pollon=0.,polgam=0. (i.e. same geographical coordinates)
               now logically (no longer pollat=90.,pollon=180.,polgam=0. or pollat=90.,pollon=0.,polgam=180.
               for geographical coordinates)

@plotmap.R@ -- this function has been re-written and includes (and thus replaces) the former
               plotmap.R and plotmap_rot.R functions. The new function now decides on the
               existance and value of the grid mapping parameter in the netCDF file .
             A new grid mapping for multiple rotated pole has been added.
             A new option is available: "na.col". The colour of undefined grid pixels is defined
               by this option. By default it is transparent.

*New functions:*
@geo2multirot.R@ -- transforms geographical to multiple rotated pole coordinates (usage: geo2multirot)
                  or multiple rotated pole to geographical coordinates (usage: multirot2geo)