TweetInfoPage: Also show the MultiMediaWidget

This previously caused the TweetInfoPage to not show the inline media if
a tweet without inline media was viewed before (and gtk_widget_hide was
called on the MultiMediaWidget).
TweetInfoPage: Remove unused variable
FavoritesTimeline: Add newly-favorited tweets
tweet-list-entry: Set correct margin-end of text_label

time_delta_label has a margin-end of 6, so we should use the same here.
examples: Generate own resources.c
tests: Generate own resources.c
examples: Fix AddImageButton example
pot update
AvatarWidget: Fix round avatar drawing
tweet-info-page: Remove unnecessary style class
tweet-info-page: Remove unnecessary widget id
Account: Don't use soup_session_send_message
Use one global SoupSession
ITimeline: Add some whitspace
DefaultTimeline: Synchronize unread_count and tweets

When we set the unread count to 0, mark all the tweets as seen.
NotificationManager: Add function to withdraw notification
TweetListEntry: Add notification_id field

And withdraw the notification if the seen flag gets set to true
MentionsTimeline: Set the mention's notification_id flag
Account: Uninit properly
compose-window: Add sizegroup back

Turns out, it *is* needed.