what's new: 1. new grid view with new layout algorithm; 2. article items updated;
to do: 1. memory management of the new grid view; 2. read and unread indicate (need to modify the database first); 3. order articles;. Fixes: https://bugs.launchpad.net/bugs/1215343, https://bugs.launchpad.net/bugs/1218201, https://bugs.launchpad.net/bugs/1218204.
Approved by Ubuntu Phone Apps Jenkins Bot, Roman Shchekin.