Open compatible solutions saved by newer Studio versions

Allow solutions saved by a newer Objo Studio version to open for normal editing and saving when their contents are compatible with the installed version. Simply saving a solution in a newer Studio should not force it into read-only mode.

Keep read-only access where the solution can be inspected safely but saving could lose unsupported data. When a solution cannot be opened or edited safely, explain which format or feature requires a newer Studio. Compatibility should depend on the features actually used by the solution.