Allow version-specific gametype support.

Allow version-specific gametype support.

It often happens when a gametype can't be supported because of
some random bug in the server code. This presents a problem
for when the bug is fixed, but servers still use the old code. We
can now specify that a game type is supported only after a certain
time by using version number restrictions. For example, CA is
supported, but only if the stats submission version is >= 5. Older
servers still having versions <= 5 won't record CA b/c they would
not pass this restriction.