Add KML datastore documentation
wfs-ng: add usage documentation.
[GEOT-4955] WMSComplexType should support parsing of the Attribution element
Merge pull request #629 from n-lagomarsini/GEOT-4955

[GEOT-4955] WMSComplexType should support parsing of the Attribution ele...
Merge pull request #630 from NielsCharlier/kml

Add KML and WFS-NG datastore documentation