Fix support for WMS overlays.

WMS overlays in google maps and openlayers is currently broken, due to
changes in argument parsing in the Maps module.
This commit fixes handling of wmsoverlay argument to be compatible with
the new API.

Also, adds extra argument to WMS for specifying wms style name (needed
for some map sources) and adds unit tests.

New changes:
Fix style issues (really fix all spacing errors...)
Make WmsOverlay compatible with other element classes

Change-Id: If425d6ade84df0397314371b1104d4e2707f0559
Merge "Fix support for WMS overlays."