Feedback about empty lists

The UX is pretty bad for all first-time users of F-Droid, because they get an empty screen and no feedback about what to expect next.

This adds the text shown here to the screen when there is nothing else to show.

It also shows a banner at the top saying "Updating repositories" whenever the UpdateService is doing its thing. This is shown on both the latest + categories screen.

Finally, it fixes up the situation where enabling only the GP repo will show a blank screen on "Latest" due to no apps being updated recently. Instead, we now show the last 200 apps which were updated from any repo.

If this can be easily rebased without including the commits from !455, then I think we should include it in %0.103 - UX Overhaul. Otherwise, since it is an improvement over 0.102 and not fixing a regression, I think it can wait for %0.104.

added bazaar label

added 21 commits

• f7daf9f2...e28e2945 - 14 commits from branch fdroid:master
• 148cc80b - Show "Updating repositories" banner in main UI.
• 5a75d643 - Adding ability to query last repo update and number of repos.
• b81f4345 - Show empty state feedback for latest + categories
• f5c7cfd7 - Try to always show something in "Latest"
• de3270ac - Extract "days since date" to Utils
• d0a7a95e - Only show "New" next to apps added in the last two weeks.
• 89b54278 - Remove unused preference "Update History".

Compare with previous version

unmarked as a Work In Progress

added regression label

added 7 commits

• dbfd2376 - Show "Updating repositories" banner in main UI.
• 20542f91 - Adding ability to query last repo update and number of repos.
• 27db9fc6 - Show empty state feedback for latest + categories
• ede096f1 - Try to always show something in "Latest"
• e57df19b - Extract "days since date" to Utils
• c36143e8 - Only show "New" next to apps added in the last two weeks.
• b3b1a110 - Remove unused preference "Update History".

Compare with previous version

@eighthave: Thanks for the review. I probably didn't need to base of !455, so I've rebased on master without much hassle. I've also tagged it as a regression because it used to show info with an empty list but now doesn't, so keen to get this in %0.103 - UX Overhaul.

mentioned in issue #425

mentioned in issue #341 (closed)

added 35 commits

• b3b1a110...01f27ac4 - 28 commits from branch fdroid:master
• d83c15d0 - Show "Updating repositories" banner in main UI.
• 510ec5f7 - Adding ability to query last repo update and number of repos.
• ab5ea39f - Show empty state feedback for latest + categories
• 3b9f8411 - Try to always show something in "Latest"
• c5051e88 - Extract "days since date" to Utils
• d41b0d33 - Only show "New" next to apps added in the last two weeks.
• 05d6929e - Remove unused preference "Update History".

Compare with previous version

Lol. I tried to make this less likely to merge by putting my new dimen value between existing values, rather than at the end of the XML file (which in my experience tends to reduce conflicts). However it just so happens that the four values that I put it between were all removed in the other branch. Should be fixed now.

merged