Add support for more than two sides for Sidebar, Speech and Loading Screens.

[CCHyper]

Closes #218, Closes #309, Closes #294, Closes #665, Closes #922

This pull request implements support/bug-fixes for the following;

• Removes the limit of only two sides allowed to have unique sidebar and speech assets.
• Removes the limit of only two sides allowed to have unique loading screens.
• Fixes a bug where the loading screen text was inconsistent, it is now centered in the text box.
• Ability to override the player's sidebar graphics. [Basic] -> SidebarSide=<SideType> (campaign scenarios only).
• Custom loading screens can now be defined per scenario, for each supported resolution.

NOTES:

Loading Screens; The original game used LOAD###C and LOAD###D for the GDI loading screens, and LOAD###A and LOAD###B for the NOD loading screens. This behavior is retained, and all further sides will use the correct suffixes (e.g. LOAD###E and LOAD###F for the 3rd side, etc).

Custom Loading Screens; You can now override the loading screen for a specific scenario. (There is a limit of 32 characters for the filename). These are to be defined under the [Basic] section of a scenario. LS400BkgdName=, LS480BkgdName=, LS600BkgdName=, for example; LS400BkgdName=LS400GDI1A.PCX

In addition to this, you can also set the position of the text on the loading screen (only if a custom loading screen has been defined); LS400TextLoc=, LS480TextLoc=, LS600TextLoc=. Each is in the format of LS400TextLoc=X,Y.