GWT-664: make zoom actions enabled correctly
Merge pull request #71 from geomajas/GWT-664_ZoomPreviousDisabledOnStartup

GWT-664: make zoom actions enabled correctly

Merge bugfix pull request
GWT-662: CanvasMapAddon + example: adding Canvas SmartGwt widget to the map
GWT-660: Deskmanager implementation of CanvasMapAddon
GWT-666: avoid warn log for change to WmsChooseLayerStep