split of alternative editor

created new subject of debat:
 1. it works
 2. checked with lint
 3. i had to change the discussed struture a bit

  TextArea<--KeyHandler<---|    a --> b  means b imports a
  ^   ^         ^          |
  |   |         |          |
  |TextAreaContentUtils    |
  |   ^                    |
  |   |                    |
  TextAreaContent----------|