Bug 847406 - Refactor call log rendering algorithm r=etienne

Based on previous work done by @ferjm in CallLogDB, this is the refactored version of 'Call-Log' based on it.
This PR includes:
- Rendering based in 'cursors' and grouping.
- Optimized rendering. No re-renderings while deleting.
- Time headers working as expected.
- Contact handlers updated properly.
- Remove weird UI effect when loading call-log.

Pending issues:
- Fix tests with new code.
- Add Contact Info to IndexedDB.
- Upgrade to V3 in DB.

Once this will be landed we will work on https://bugzilla.mozilla.org/show_bug.cgi?id=847409, adding infinite scroll.