Various things, listed in description.

* A few doc comments.
* Progress bar shows how many .game files have been processed.
* Progress bar says what task is being performed, still no percentage
for downloading and unzipping.
* Everything in actionPerformed put in a separate Thread so as to not
freeze the GUI.
* Game's constructor get the installed version from the .game file, then
downloads the newest version of the file before getting the rest of the
information.
* Small GUI changes.