[BREAKING CHANGE] Debug bar refactor

Move DebugBar from init to ui and set it up like we do
with toolbars.

* Move this.surface setting to constructor
* Change demo to create a new DebugBar on every page load
* Move setupToolbar into ve.init.Target from MW
* Rename setUpToolbar to setupToolbar

Change-Id: Ied519093723b76e6ed531e6188ee7848d4f0923c