Gamepad fixes & changes

Resolves a number of small gamepad issues that popped up since !1870 (merged):

• Fixed gamepads not being able to skip the tutorial prompt
• Removed "Controls per key" setting, now duplicate bindings are always checked but per-player
  • This fixes P1 gamepad bindings being cleared upon second game load, due to gamepad buttons having the same names for both players now
• Added a list of old gamepad key names to convert, so existing gamepad bindings get converted instead of being wiped

Also includes several changes to default gamepad controls:

• Center View has been changed from R3 (right stick click) to R1 (right bumper) (resolves #813 (closed))
• Chasecam toggle has been changed from D-Pad Up to L1 (left bumper)
• Prev/Next Weapon have been changed from R1/L1 to D-Pad Left/Right
• Toss Flag has been changed from D-Pad Left to D-Pad Up
• View Scores (Tab) has been changed from D-Pad Right to D-Pad Down
• Next Viewpoint (F12) has been changed from D-Pad Down to R3 (right stick click)
• The default Look Up/Down axis has been changed, to prevent vertical camera movement from being inverted

Additionally includes some cleanup:

• Removed some input-related code that was only used for really old configs (pre-2.1.22)
  • Renamed G_FilterKeyByVersion to G_FilterSpecialKeys, since that's all it does now
• Removed jump/spin/fire/firenormal axis cvars & menu settings, since sticks & triggers can be bound normally to these controls now
• Added menu option name enums to main options menu & data management menu, as a safeguard against crashes when these menus are changed