Admin controllers

This PR has a higher-level (file/class/function) redesign of most admin controllers, to object oriented controllers, and a few rewrites of methods. It's another step (or a few of them) in preparation for the MVCish code design we target.

I'm not sure we want it in as it is, since some aspects are very basic (and it looks terrible :P).
Update0: well not that bad anymore.

Note: the issue of forwarding directly to actions is still unsolved in this PR, updates of the menu and dispatching mechanism will be necessary for that, apart from more fully OOP controllers. (more than this)

On yet the brighter side, most of these is what will stay (tm). :)

Update1: I added the previous branch on @emanuele45 's Settings... Which I'm not happy with... yet.
Update2: admin is almost finished with the current changes. Settings_Form is being used in admin, for settings pages. The class is used through its interface thereby allows for internal changes to improve it or replace it completely, as long as it behaves the same on the outside.

Update3: I added Action class. This is a small class used to 'know' the actions and subactions of the current request, the permissions for them if any specified, the default sub-action to execute, and potentially a few other things like this. The class is meant to get all common code of the sub-actions handling, in one place, and forward to the appropriate method for the current request. (a dispatcher/router at the level of controller, as the dispatcher class is at the level of the entire site).