CMakeLists.txt: Remove unused compiler options
Add DoubleTapButton

Which is an ordinary GtkButton which needs to be activated twice in
order to actually invoke the action associated with it.
Remove follower.png/svg

which is nowhere used anymore
Utils: Make show_error_object more robust

It now also works if the json stirng is malformed(in which case the
alternative will be shown).
Also, if the josn data does not contain an 'errors' array, but just an
'errors' string, we simply show that.
TweetUtils: Use show_error_object more often
Use a DoubleTapButton as retweet_button
Merge branch 'master'
Merge branch 'master' into double-tap

Conflicts:
	src/util/Utils.vala