AppSettings/FGManager: Block VSFilter when XySubFilter will get used

CLSIDs for VSFilter and XySubFilter have now been added to
moreuuids.h, which is now included in AppSettings.cpp, where the
IsVSFilterInstalled() function used to utilize the string.

FGManager now utilizes the added CLSIDs as well, as well as blocks
VSFilter when XySubFilter is registered, and MadVR is used as
the renderer (in the future the amount of things in the check
might have to be adapted depending on the implementation of MadVR's
subtitle interface).

There was an idea about disabling xySubFilter when the ISR is
usable and enabled, but since the renderer is supposed to load it
for auto-loading of subtitles not provided by splitters, setting a
"do not use" merit in FGManager will not have any effect on the
result.