Add a resource exporer view.

[UrsZeidler]

The model exploerer of the ecp model explorer is a generic components, and fits not very well in the base product.

We need another resource view to browse the model

• treeviwer with context menu to create sub elements
• search panel for name filter
• a nice structure for the character object
• display the validation result
• hiding the language node

[NoxMortem]

Especially the name filter is important as this helps to test the resources and fix problems as it avoids the "Open object/item" redirection.