Numerous changes to help screen lumps

* "HELP" title in DOOM II
* Change "map" to "automap"
* Change "pause key" to just "pause"
* Add "printscrn = screenshot"
* Add "alt + enter = fullscreen/window"
* Change "mwheel" to "mousewheel"
* Drop all instances of "gamepad"
* Add use of "button"
* Change "btn" to "button"
* Change "thumb" to "thumbstick"
* Minor corrections