Improved viewport sizing for both Desktop and Mobile Firefox

Features:
- Basic support for wordpress-based blogs (derived feeds)

Fixes:
- Special symbols are displayed correctly now
- Corrected text ellipsis for some corner cases

Fixed 3rd party opener URL settings restoration.

A couple layout fixes

New version also supports unofficial feeds for some popular websites, like YouTube.
It means that the feeds are not listed directly on the page but are instead derived from page content using official APIs.

Unlike official feeds, unofficial ones may break if there are changes to the website or its RSS API interface.

Currently supported:
- YouTube
- Reddit

Further improve mobile layouts in different cases.

Fixed layouts for Firefox Mobile