[TUI] Refresh single feed

[bacardi55]

Ability to refresh a single feed. This could be useful in 2 cases:

• After adding a new entry, only refresh our own tinylog.
• When looking at a single tinylog, to accelerate the refresh for the current feed.
  The idea came from szczezuja

While I like the idea, it has a few issues for me:

• if I refresh only 1 feed (mine or any), then I have feeds not refreshed at the same time. It causes 2 issues:
  • Incoherent timeline: When switching from 1 feed to all, then I may have a item from 5min ago from one feed but may not see an item from 10min ago from another feed unless I refresh when switching back to all feeds.
  • Incoherent refresh time: Refreshing individual feeds means having an individual refresh time for all feeds and then it becomes a mess to pass that info cleanly to the user without bloating the UI…
• In case of "refreshing my tinylog after adding an entry": gtl does not know which feeds is yours. Many users may not add their own tinylog to avoid seeing their message all the time and focus on other (reason of the mute option too). But even if the author tinylog is in the subs file, it will not know which one it is. I could add an specific option for this, but based on above issue I don't think it's worth it.

For these reason, I don't think I'll add this in the short term.
The main reasons for this is because right now the UI is blocking while refreshing and that may be annoying but, for this one please see #25