add mechanism that visually marks abstraction objects that are edited but unsaved (dirty)

add mechanism that visually marks abstraction objects that are edited but unsaved, and all their ancestors. This feature allows the user to easily identify the location of unsaved but edited abstractions that could cause problems and unwanted behaviour.

Was originally included in the WIP patch 'patch private abstractions [ab]'. It has been separated because it doesn't belongs to it, conceptually.

Preview:

The colors can be changed if red and orange are not adequate.