RichTxtEdit

A test, exploring rich-text editing without the use of iframes
Firefox only at this stage.

Currently trying:
* Allow type-insertion
* Make bold (control-b)
* Make italic (control-i)
* Backwards deletion (delete/backspace)
* Delete selection (delete/backspace)
* Key events limited to txtedit areas
* Navigatable using left & right keys (← / →)