Remove posteditor.js

Current trunk includes "posteditor.js", which is not only responsible for JSPWIKI-380, the licensing also does not allow it to be included in an Apache project.

The licensing conditions say exactly:

License:
MIT-style license.

However, this is not legally binding at all - the license conditions MUST be explicitly stated. "MIT-style" could mean anything...

Therefore, I propose we drop posteditor.js and all the related functionality asap.