Need to Remove EAX references from UI

[patmauro]

EAX is dead and is not coming back - so even though there is an ongoing effort to emulate these via EFX, it would still be prudent to remove the references in the UI to the EAX technology specifically, especially given how much of Uru's sound logic has already been ripped out in favor of OpenAL.

Specifically, we need to do the following:

• Remove the EAX graphic at the bottom of the Audio Settings menu.
• Either hide the "Enable EAX" option outright until an EFX solution is ready, or simply replace the string with "Enable EFX," and allow this to similarly be greyed out until an EFX fix is ready.
• Since this is a UI change, the changes should be done via xKIGUI.max.

PR #239 attempted to solve this issue by replacing the EAX graphic with an OpenAL graphic and by directly modifying GUI_District_AudioSettingsDialog.prp to change the "Enable EAX" string to "Enable EFX" - however, the feedback was that (A) we should instead remove the graphic outright, and (B) the needed changes should instead be made in xKIGUI.max and reexported afresh so that the source files can reproduce the game files exactly.