#580, last page notifications

[Adamantcheese]

Fixes #580. Relies on the solution done in #252 for some functionality, which is included in this branch.

[Adamantcheese]

At this point I'm not going to submit any other pull requests. I think that the 8 I put in are plenty more than enough. If anyone's reading this, they can find a debug multi-release of all the features from the pulls here.

[TacoTheDank]

@Adamantcheese
Nice job on all of these :) I've been getting antsy for a new dev build, so I'll download the apk and try it out.

One feature that would be great to see is a thread and setting backup and restore function, like how the Reddit Slide app does it (I believe this and this are the code files for this function). Would this be too much to ask? This is merely a suggestion I feel you have the skills to implement now instead of everyone having to wait until Floens eventually gets around to it, but feel free to decline if you don't want to do it.

[Adamantcheese]

I've made a fix that makes last page updates quicker, due to an oversight. You can grab that new release at the link above.

Previously, in the background, pages would be requested, but not used until the next time interval. Basically, an interval of 15 minutes would actually mean 30 minutes; the first request at 15 minutes would be to get the pages and the second request at 30 minutes would be to actually send the notification, as the pages in the previous request hadn't been processed when the first interval was fired off. In additon, the request would only be for one pin.

Now, it's set up with a callback; if you request pages, it'll message the requester when the pages get there and should send the notification immediately. Also, one page request is for EVERY pin now.

[Adamantcheese]

I'll take a look, but I give no guarantees. That would fall under the slew of "add an archive" requests. Submit a new issue for your feature request.