#153 Workbench creation

[Skalpa Keo]

I'm going to start working on this during the next
days, sharing my time between this task and other
things I have to do (I need to have something to code
when I don't feel like doing anything else).

Objective of this task is to make the future admin
reorganization easier. Like what was done in the
installer, nothing entirely revolutionary is supposed
to be implemented, it's more a preliminary step
(although it will already bring welcome
enhancements).

What's actually the "administration" will be split
into 3 sections:
- Control center (for system configuration)
- Admin tools (non-settings related, additional
functionalities, like the installer)
- Workbench (for the pages that belong to modules)

Behind the scenes, as little changes as possible will
be performed, to ensure the patch generates as little
problems as possible. The only real novelty will be
that the "workbench" section will be managed by a new
module, independent of the "system one" (one later
objective in future version will be to allow sites
owners to keep the workbench module, and remove the
system control center from their live sites for
enhanced security).