Draft: improve inventory resource display
- change tree-drawing characters
- add defaultNamespace to TreeInformer, introduce DisplayName() and use in 'watch'
- extend tree module with Tree.Context()/GetContext()
- internal/inventory: add InventoryOptions.OmitNs, propagate it in Tree Context, use in Text() for printing
- use InventoryOptions.OmitNs in 'watch' and 'inventory' commands