enable ot for rich text editors

a small re-factoring of forms.js which make rich text editors handling similar to basic textareas, main changes are:
- a common function used to send all editors updates (`sendData`), deltas are calculated using Textreplace for all editors rather than specific editor delta representation.
- storing this.element as HtmlElement in the tracker object and use jquery only when necessary ( to avoid confusion).
- add ckeditor support

this will basically make adding support for new editors fairly simple, however, not very efficient solution way since many editors offer native and more efficient interface to get delta, also, when a form-update received, the whole form content have to be reinserted (some editors optimize this internally) 

some other changes need to be made after this commit like updating tests, but I want to discuss this commit first before dig deeper into the code.