Issue/1730 reader detail infinite scroll with blocking

Fix #1675 and fix #1730 - adds "infinite" scroll to the reader detail ViewPager and adds the ability to block a blog from the same view. This was initially submitted as separate PRs, but they rely so heavily on each other that it made more sense to combine them.
I'm not too familiar with how blocking works, but I'm wondering why I can't block a private post?