Adds a way to disable the stroke of a RecodedArea.
Tested to be sure we don't have NPEs.
Let's take care of null a bit more...
Adds management of null stroke for recoded area in the UI
It's possible to enable and disable the stroke for unique value
classifications made with area symbolizers.
Merge pull request #358 from agueganno/improvement/Stroke-for-area-classif

Management of stroke in unique value classification for area