[FIX] m.DatePicker unneccessary change event if value was set to null

Change-Id: Ia05d24917be1b37707a6befd7c52efa2617abfb0
BCP: 1482023605
[FIX]m.Toolbar: Float should have no effect on a flex item.

- Empty width should return instead of auto when control width is not
found.
- Cleanup for hand-over.
- Toolbar header font size fix.

Change-Id: I6157a2fcc10025d8b554a1778f70a7db38fbcc21
Merge "[FIX]m.Toolbar: Float should have no effect on a flex item."
Merge "[FIX] m.DatePicker unneccessary change event if value was set to null"