Implement grammar editor
- viewing includes application of the grammar against sample input
- editing should include some minimalistic versioning mechanism in order to not immediately save new grammars with the container
(from redmine: issue id 314, created on 2018-01-22tgradl, closed on 2018-01-22)
- Relations:
- relates #317
- relates #297
- relates #318
- relates #321
- relates #322
- relates #323
- relates #324 (closed)
- relates #326 (closed)
- relates #334 (closed)
- relates #354
- relates #355 (closed)
- relates #356 (closed)