See https://blogs.gnome.org/hughsie/2018/02/16/ for more details.

Any bigger jump is unsupported by Fedora and likely to not work right.

This will avoid having to check three app states all the time.
Signed-off-by: Richard Hughes <richard@hughsie.com>

Based on a patch by Iain Lane <iain@orangesquash.org.uk>, many thanks.

This means we can refine large lists of apps without doing multiple requests
to the server. Also make sure the data exists when starting as we'll soon
switch to requiring reviews in more places.

All the ratings are re-downloaded every 30 days.

This fixes the following valgrind warning:

==22489== Thread 6 pool:
==22489== Syscall param access(pathname) points to unaddressable byte(s)
==22489==    at 0x8E0B7A7: access (in /usr/lib64/libc-2.22.so)
==22489==    by 0x82DF366: g_file_test (gfileutils.c:409)
==22489==    by 0x1DF54212: gs_refine_item_pixbuf (gs-appstream.c:72)
==22489==    by 0x1DF54212: gs_appstream_refine_app (gs-appstream.c:582)
==22489==    by 0x1DF54CAE: gs_plugin_refine_from_pkgname (gs-plugin-appstream.c:311)
==22489==    by 0x1DF54CAE: gs_plugin_refine_app (gs-plugin-appstream.c:362)
==22489==    by 0x1506AE: gs_plugin_loader_run_refine (gs-plugin-loader.c:196)
==22489==    by 0x152B10: gs_plugin_loader_search_thread_cb (gs-plugin-loader.c:1491)
==22489==    by 0x7D5CD6C: g_task_thread_pool_thread (gtask.c:1287)
==22489==    by 0x831A27D: g_thread_pool_thread_proxy (gthreadpool.c:307)
==22489==    by 0x83198E4: g_thread_proxy (gthread.c:778)
==22489==    by 0x8B02619: start_thread (in /usr/lib64/libpthread-2.22.so)
==22489==    by 0x8E1B59C: clone (in /usr/lib64/libc-2.22.so)
==22489==  Address 0x0 is not stack'd, malloc'd or (recently) free'd

Resolves: https://bugzilla.gnome.org/show_bug.cgi?id=768420

Richard Hughes authored Jul 08, 2016 and Kalev Lember committed Jul 12, 2016

In this case the results object is nonvalid and the PK error is set.