Joystick configurator

This is the joystick configurator discussed in this thread: http://aegidian.org/bb/viewtopic.php?f=6&t=16162.

The main joystick option screen has a new option to edit axis profiles:

![oolite-016](https://f.cloud.github.com/assets/5890866/1938876/31a41196-7f55-11e3-84ad-fdc9f2c65372.png)

which enables the player to configure the joystick response to taste.  There are two types of joystick profile; "standard", which is a curve with two tweakable parameters:

![oolite-017](https://f.cloud.github.com/assets/5890866/1938888/6ba1b114-7f55-11e3-8d1f-a31722f84032.png)

and "spline", where the player defines the curve by setting control points using the mouse:

![oolite-018](https://f.cloud.github.com/assets/5890866/1938890/84dee1e2-7f55-11e3-9b7b-2768dcfed5cc.png)