TweetListEntry: Move inline tweet buttons to the top
TweetListEntry: Remove GtkOverlay

... and move the inline buttons in the upper part of the entry.
TweetListEntry: Hide the conversation_label on hover
Merge branch 'master' into tweet-buttons2
TweetListEntry: Fix more-button label

...and remove the margin_end that slipped in last time.
MainWindow/switch_page: If cur_page == page_id, just call on_join

... it won't be accessible via the back button, but it's still better
than our current approach of just ignoring it.
TweetListEntry: Try to use a GtkOverlay again
TweetListEntry: Let the hover box draw a background

This way, when hovered, the hover_box will just shadow the
screen_name_label which is often beneath it.
TweetListEntry: Decrease the space between username and text
TweetListEntry: Use the link in time_delta_label again

... also, remove some left-over unsused variables
TweetListEntry: Remove old variable
Merge branch 'tweet-buttons4'

Conflicts:
	ui/tweet-list-entry.ui