server, browser: partial Libervia fix Libervia was broken following the refactorings. This commit partially fixes it : Libervia is starting, avatar, blog and message are working again, but not everything is restablished yet. following things have been fixed/changed: - new dependency: shortuuid - D-Bus bridge is working again - fixed naming in several bridge methods - register method changed to register_signal - fixed Chat widget, which was not working anymore since the refactoring - avatar now use avatarGet. Cache dir is accessible using a session specific uuid, to avoid cache leak (i.e. accessing cache of other profiles) - server: new uuid attribute in session data Browser code is not fully working yet, notably OTR and contact list are not fully fixed.