Rethink and refactor mapping sync
- grammars were lost before, now they are always reimported
- what about deleted grammars?
(from redmine: issue id 1176, created on 2018-08-29tgradl, closed on 2019-05-14)
(from redmine: issue id 1176, created on 2018-08-29tgradl, closed on 2019-05-14)