Update report when ABS files are modified
When an ABS file in the project (or imported by URI if implemented) is modified, it should be reflected on the report.
At first, just deleting the report when an ABS file is change should be enough to avoid bad states.
Ideally, we would want
- If the system is modified (only if its semantics may change), all witnesses should be marked as obsolete (or deleted)
- If a goal is modified (pre/post), all witnesses for this goal should be marked obsolete
- changes in goal names should be reflected in the cross-referrence (if it is not deleted)