minro edits in index.rst, ipol.rst, verify.rst, verify.py

minor edit

still experimental map plotting in vis.py and vis_example.py, please do not use, yet

added a class to verify.py which extracts radar bins in the neighbourhood of a rain gage,
added a corresponding example workflow in verify_example.py

bugfix in georef

adding a basemap plot of polar radar data to vis and vis_example - still
needs refinement. This is just the outline. This plot type allows polar data to
be plotted on arbitrary map projections including shapefile overlay.

some refinement of the example for georef

lots of changes in georef and the corresponding example: introduced a new
approach for computing the polygon vertices and a more explicit method for
computing the centroids of the bins. But both are founded on polar2latlon

added a new function polar2polyvert in georef.py which does not use centroids
to compute the polygon vertices

added an example file georef_example.py which should contain a workflow for
georeferencing radar observations only from the location of the radar and its
azimuth and range specs

added projection examples for UTM

added necessary imports

added the project function to georef.py,
I hope the bad merging problem is now resolved...

merging went wrong, trying to recommit thomas revision no 83 and then late the new changes from me

merge conflict - removed conflicting function for while being

added funciton to convert lat/lon coordinates to native map coordinates (projection)

changed the rotation properties of the polar plot

changed the rotation properties of the polar plot

substituted the dictionary for attenuation coefficients by direct
parameterization.

some docstring changes