Remove the need for panels in edit mode

Implementation of XSCOLIBRI-179 brings the question of the need for panels in edit mode.
We've talked about removing them for a while and we're now close to be able to do it.
Sergiu and I have recently worked on the edit mode without panels, you can see a preview of this work at http://incubator.myxwiki.org/xwiki/bin/view/Improvements/ImprovedEdit