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.
