Update lists

[di72nn]

Adds "endless scrolling" instead of limited list. Memory may still be an issue.

Use DiffUtil to update lists partially.

I'm not completely sure about the implementation, so suggestions are welcome.

Also, I think I had an issue with the lists not being updated after actions like "open an article - add it to favorite - go back to lists". I couldn't reproduce it yet. I added logging of warning messages "fragment is null". I'm pretty sure it should either update list or log the warning. I have no idea why the fragments can be null after they were initialized (initially I thought, that it might be related to threading, but only the main thread is supposed to access fragments). Probably fixed with 2630998.

Related issues:

• Basic search: partly Search #113.
• Sync queue before full update: [1.9] Combine URL upload and sync #127.
• Sorting order: partly Sorting mode of the articles #17 and Sorting modes of article list #42.

Testing needed.

[di72nn]

Added basic search (using SQL's LIKE %search string%) on article title and text.
Current list is updated on every search string change - not sure about performance.

[tcitworld]

Hmm. I guess it will provoke some performance issues with huge articles, some maybe limit to title for now. Anyway we'll probably propose a search API soon on the server so it will have to be integrated with it at some point.

[di72nn]

Added an option to reverse sort order. The UI part should probably be improved (as for now it is just a menu item that reads "Change sort order"). Suggestions are welcome.

There is an issue that fragments reinit their lists after orientation change. It is not critical (slight delay), but I'll have to fix it. Fixed.

[di72nn]

Started to use AsyncTask to update lists. Synchronization issues are possible. Removed from this PR.

[Strubbl]

is the read to review label still valid atm?

[di72nn]

I removed the async loading from this PR - now it is ready for review.

[tcitworld]

Looks good. Will review and eventually build tomorrow.

[di72nn]

@tcitworld

Hmm. I guess it will provoke some performance issues with huge articles, some maybe limit to title for now.

I forgot to answer that. It seemed to me that the performance was decent even on old devices, so I left it as is. I considered "powerful" search (being able to search in content) more important than minor performance issues (which don't affect anything but search). Though, anyone is free to improve the feature.

[tcitworld]

I tested and it was okay for me so I merged. :)