Added utility methods to manage gp layout
The scale widget is displayed in central panel and it is draggable, it acepts users inputs
Added layout properties to configure client aspects
Added various usefull methods to manage the geo-platform panels layout in terms of number
The layer panels: legend widget and layer tree  can be disposed using the property file indicating the west panel or the east panel
Merge branch '1.6.x' of https://github.com/geosdi/geo-platform into 1.6.x
Setting the default layout property to zero for layer tree position