Input manager for advanced inventory

This PR converts the entire advanced inventory to using the input manager. This means, all the key bindings can now be viewed and reconfigured.

Detailed changes:
* Normally I tried to stick to the original keys, but I had to change a few key bindings to avoid collisions
* Category toggle is now `c` instead of SPACE, because SPACE is used for quit already.
* Pressing the `?` key now opens the input manager dialog.
* `UP`, `LEFT`, `RIGHT` and `DOWN` are defined **locally**. This is because the global bindings also use numbers, which would cause a collision to the field selection.
* The upper section is now solely for protocol messages, the fixed input help has been completely removed

Weirdness:
* For some reason, when opening the input dialog, the entries “Pan up” and “Pan down” (`UP` and `DOWN`) appear twice. I have no idea what causes this. (Edit: Fixed!)
* There are still texts like “[s]ort”, even if you can rebind all keys now. I think I should change the strings to be more general. The biggest problem would probably be the field selectors [1], [2], etc. Any suggestions?

I have tested it a bit and it seems to work fine so far, except for the small weirdnesses mentioned above. However, further testing and comments are always appreciated!