[Skin Expansion] Initial R_InitSkins tweaks and GetSkinInfo ACS function

Part 1 in Splitting this up into smaller commits.

• R_InitSkins tweaks such as making 'key' an FString instead of a char array, and SKININFO parameters spaced apart and commented between each in the code to improve readability.
• szColor in sprites.h renamed to color
• Duplicate names are now checked within the skin's class's skin list instead of every skin.
• You can no longer name a skin "skin" followed by a number (e.g skin2, skin32, etc.)
• 'color' parameter now uses V_GetColor and stores an integer.
• 'scale' parameter can now set x and y values separately using a comma.
• New SKININFO param - colorrange which overrides the classes own unless the class uses 0,0 which usually signifies that there is no color translating for that class.
• GetSkinInfo(int skinIndex, int type, string key[, int index]);

  • For int type:

    • GETSKININFO_STRING (0) returns a string or "" if null.
    • GETSKININFO_INT (1) returns an integer or -1 if null.
    • GETSKININFO_FLOAT (2) returns a float as a fixed number (i.e 1.0 = 65536) or -1 if null.
    • GETSKININFO_EXISTS (3) is a boolean to see if the key[index] exists for the given skin index. Useful for conditional statements.

  • Custom Values are supported, which can be a single parameter or an array.

    customparam = "Something"
    customarray = "Stuff", "More Stuff" 

  • They can also be put into a group using square brackets.

    paramgroup = [
    key1 = "value1"
    key2 = "value2-a", "value2-b"
    ]

  • Parameter groups are formatted as such: "paramgroup:key1" in string key, which also means colon (:) can't be used in custom parameter names.

• GetPlayerSkin now returns the skin index instead of the name in order to be interfaced with GetSkinInfo.