Unlock key bindings for Esc and F-keys

[xenojeff]

Why are those keys locked? 

The Esc key is inconvenient to use to exit menus in the game.  I would like to bind the exit key, as I do in many other games, to one of my extra mouse keys. 

Also, F5 and F6 are too close to each other to use for save and load game.  A few times now I've saved the game instead of loading it, and it messed me up.  This is the first game i've played that doesn't allow rebinding those keys. 

Thanks!