Tweetview rework

As previewed in #111
Also fixes Favorite star icon not showing up on tweetpage.
Fix loader comment

Not sure if this is less complex, as visible property didn't de-allocate
space it used. So I had to force that with some further checks in
TweetDelegate. See line 109 and line 120.
Merge pull request #114 from Morpog/sailfish-port

Tweetview rework