Changed the way editor is closed during the update process (updater now asks to close the editor after downloading the update package).
Added write access check before performing the update.
The editor can now update the updater.
Updater: merged relevant parts of SharpCompress into the updater source, reducing updater file size from 900 kb to 150 kb.
Updated ZDoom_DECORATE.cfg.
Updater: error messages now display more info.
Updater: editor closing step is now performed after downloading the update.
Updater: added taskbar progress indication.
NOTICE: to obtain the updated updater, you'll need to download GZDB manually from http://devbuilds.drdteam.org/doombuilder2-gzdb/, because the updater can't update itself.
Added Updater source.
