Added --avi option

Re-mux video to AVI container
Added --mp3 alias for --aactomp3

Also moved MP3 options to Output section in help
Added --hfsfilename option

--hfsfilename will remove colons in file and directory names.  The only
purpose of this option is to prevent OS X Finder from displaying colons
as forward slashes.

Also tightened up --fatfilename processing and corrected --whitespace
help text.