New menu system

[thelusiv]

The Calibrate widget is now mostly done (r987). It draws the way I want it to, minus the text it needs to display. Currently it displays up to three grids, each representing two axes. You can move your joystick axes around and see the cursor move around on the grid. There is no visual cue yet for where the calibration points are set, this needs to be done. It was tricky to do this, but I made it so that if you haven't moved any axes yet, it doesn't display anything. if you move one stick (two axes) it will display only one grid and cursor. If you move another stick it splits into two grids with two cursors, one for each stick.

Screen shots:
before movement
after movement of 1 joystick (2 axes)
after movement of 2 joysticks (4 axes)

Bugs:
* for some reason joystick move events are not generated when the joystick is at 0, so the joystick cursor never actually crosses the grid axes.
* if you mouse over the cancel or ok button the calibrate widget no longer responds to joystick movement
* the gui is not yet aware when a calibration has been done, so it still doesn't allow you to add joystick controls or use the joystick in the menus even though you've calibrated.

Stuff to add:
* a way to change to and calibrate the next joystick(s), if there's more than one
* text displaying which axes are where
* some sort of visual cue showing where the upper and lower boundaries have been set
* in-game joystick calibration menu needs to be added
* it'd be nice if the calibration widget reacted to the joystick deadzone so you can get a feel for how much of the stick range is usable before playing