* The level.FileSystem type has updated to support ZIP files too.
* Legacy levels loaded from gz/json have their old FileSystem as a
simple map[filename]data and this parses from JSON OK.
* On save to zip, the legacy loaded file data gets exported to ZIP.
* Going forward: newly added or deleted files during runtime are kept in
the legacy file map until the next save when the filemap is again
flushed out to ZIP.
* For regular read-access, the FileSystem reads from the ZIP file if the
data is not in the hot map (legacy file or recently modified
attachment).
* Bugfix: be sure to Inflate() the Level/Doodad after loading from
zipfile - it used to be that directly after a save, trying to play the
level failed because the Level.Actors struct was missing their IDs,
and similarly recently written chunks would error out (become black
voids) on levels/doodads so we Inflate() both after save/replacing
their zip handle.
Noah Petherbridge
402b5efa7e