separate sync methods for photos albums, and tags
Sync albums and tags on open
pause photos sync when view will disappear
fix sorting. add new symbol to icon font
async view extension registration
create the flattened view when creting the group. fix crash exc_bad_access on receiving notification.
fetch next page after db insertion complete. change nslog to cls_log.
change sorting button
scroll to top when changing sort
album sort
fix scrolling to top crash after changing view mapping.
Tags sort
set selected sort
pass the created view mapping directly to horizontal photos so that transition is faster.
Merge branch 'feature/paging_syncing' into develop