✨ direct support of plantuml diagram view for Asset and AssetType in xtext editor
When clicking in xtext, the plantuml view is updated to show an excerpt of the model.
- When clicking in a file with Assets: it shows all the relation between the assets of the file
- when selecting an Asset: it shows all related assets across the resourceSet (pointing from and to this Asset)
- When clicking in a file with AssetTypes: it shows all the relation between the assetTypes of the file
- when selecting an AssetType: it shows the AssetType and all its parents and the outgoing references from them
Note: that is several diagrams are applicable, they are available in the "3 dots" popup menun of the plantuml view
Closes #410 (closed)