Added a 'convert' function to RasterSource
Added fromString to Extent
Doc string was wrong.

The problem with doc strings is that they can sometimes be misleading!
Fixed geotools tests
Moved version up to 0.9.0-RC2
Created CanBuildFrom from ValueSource[_] -> RasterSource

This is for mapping a ValueSource to a raster, for instance if you
rasterize a polygon, you should get a RasterSource back.

Changed the .info on RasterSourceLike to check if the definition is
for a catalogued raster; if so, pull the info from the catalog, else
build an info off of the raster definition.
Merge pull request #702 from lossyrob/0.9.0-RC2

0.9.0 RC2 changes.