Improvements sharing usefull code betweeb client and server
Conflicts:
	geoplatform-gui/core/geoplatform-widget/basic-widget/src/main/java/org/geosdi/geoplatform/gui/client/widget/tree/GPTreePanel.java
	geoplatform-gui/core/geoplatform-widget/layer-widget/src/main/java/org/geosdi/geoplatform/gui/client/widget/tree/builder/LayerTreeBuilder.java