Implement mapping editor

Implement mapping editor based on old mapping editor (ScheReg v1) and new schema editor

(from redmine: issue id 396, created on 2018-01-22tgradl, closed on 2018-01-22)

• Relations:
  • relates #398 (closed)
  • relates #397 (closed)
  • relates #407 (closed)
  • relates #408 (closed)
  • relates #418 (closed)
  • relates #419 (closed)
  • relates #420 (closed)
  • relates #423 (closed)
  • relates #424 (closed)
  • relates #426 (closed)
  • relates #427
  • relates #428