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)