Additional code cleanup in libraries and includes

Most significant changes are the removal of the outdated
ciftree_games.hpp, and renaming offset.hpp to crypt_misc.hpp
Factor out avfdec stuff into library functions.

This makes avfdec_main.cpp look a bit saner. Still needs to be made
consistent with the other utilities in terms of arguments supplied to
the commandline.
Add commandline parser

Doesn't support flag grouping, values are specified as either -kvalue,
-k value, --key=value, or --key value. Also supports -- to turn off
named argument handling.

May not be approprite as part of the library, but for now it's a good
place to keep it.
Make all utilities use commandline parser.

Allows for some nice uniformity between them. The only big change left
is to make filesystem operations sane, which requires using the
filesystem stuff from TR2.

... or rather, since TR2 isn't yet official, we'll use boost's
filesystem library /for the time being./