Key refactoring, important changes:
* Add cursor below/up is now Ctrl-Shift-Up/Down (instead of Ctrl-Alt)
* Add cursor on next/prev instance is now Ctrl-Shift-]/[ (to be more consistent with Ctrl-[ and Ctrl-])

In addition a lot of Alt- based keys were added familiar for vim users, e.g.:
* Alt-h,j,k,l,0,$,^,w,b all do what a vim users expects (and versions with Shift are the selection versions).
Added Select:None command.
Fixes and tweaks