Introduce EnablesStroke, OnVertexOnCentroid

These were two interfaces that I really felt were missing. Note that
this removes a lot of unnecessary javadoc and replaces it with the
@Override annotation.
Use the new interfaces to reduce code

Using these new interfaces, we don't need to override the postProcess
method in four different classes. Note that both if statements evaluate
to false in PnlCategorizedLine and PnlRecodedLine.
Merge remote-tracking branch 'adam/suggestion/alexis' into vertex_imp

Conflicts:
	orbisgis-view/src/main/java/org/orbisgis/view/toc/actions/cui/legends/PnlCategorizedArea.java
	orbisgis-view/src/main/java/org/orbisgis/view/toc/actions/cui/legends/PnlCategorizedPoint.java
	orbisgis-view/src/main/java/org/orbisgis/view/toc/actions/cui/legends/PnlRecodedArea.java
	orbisgis-view/src/main/java/org/orbisgis/view/toc/actions/cui/legends/PnlRecodedPoint.java
We're aiming to keep properties on new analysis
let's keep UOMs too.
Adds some fields in PnlAbstractTableAnalysis.
This lets us keep UOMs when enabling/disabling stroke in areas and
points.