This goes along with the ability to "go to" a saved hashtag timeline.
We need to pass the "local" flag down build_timeline() method so that
this is also saved. Note that we cannot save both a local and a
federated timeline for the same hashtag: I'm not sure it's worth
supporting both options?
We introduce "saved timelines" as a new entry in configuration file. For
now, we only save whether the timeline is local or not. Timeline save is
not implemented yet, only retrieval from config file and display is
handled at the moment. Saved timelines in the goto menu.
We add a new [L]inks action that opens an overlay window with links
found in the content of selected status. Links are selectable and upon
click/enter we open the web browser at link's URL.
