Game settings screen, and minor fix on discordRPC

- Uses BG previously from the input config screen, which has gotten a new BG
- Minor tweak on the input config screen to display all inputs names regardless of if they are bound or not
- Added Mod1 function to `funcs.lua`, may be useful again sometime
- Added game settings
  * Manual locking (per gamemode, per ruleset, on harddrop or on softdrop)
  * Piece colours (per ruleset, TTC or Arika)
  * World Reverse toggle
- Moved the discordRPC `libs/` directory, as it's a third party library
- Edited the `discordRPC.lua` file to look for the dll at the right place regardless of how you run the game (until we fuse it that is)

This should have probably been done in several commits, sorry about that

funcs.lua

@@ -61,4 +61,9 @@ function formatBigNum(number)
 	if pos == 0 then pos = 3 end
 	return string.sub(s, 1, pos)
 		.. string.gsub(string.sub(s, pos+1), "(...)", ",%1")
+end
+
+function Mod1(n, m)
+    -- returns a number congruent to n modulo m in the range [1;m] (as opposed to [0;m-1])
+    return ((n-1) % m) + 1
 end