fix the unregister_account bug

dnspython target returns with dot in the end. catch and fix that; thanks della for helping me and reporting this

check for new version [one of the first thing I did for Gajim :)] is not needed anymore as most distros have us. remove it. this also means we can now update Changelog periodically in svn. YUPPIE!

until we find a way to detect snaps from releases revert a commit I did some weeks ago to assist Yann release .exe faster

 * we now migrate automaticaly at startup in a thread
 * progressDialog now scroll textvew to the end

take into account only the accounts that are synced with global status to compute the global status (for status combobox)