Fixes sometimes drawing tabbar while restoring is in process, resulting
in painting only few tabs and then all restored tabs after a moment.
It will now only draw completely restored tabbar.
Also fixed one incorrect usage of setUpdatesEnabled in TreeWidget.
- you can add subscriptions in AdBlock dialog or with
abp: scheme links
- however, AdBlock rules are not yet optimized for performance
so you shouldn't add too much subscriptions
performance optimizations will come in next commits
- support for element hiding is still yet to come too
closes#266
