Fix margins between headers and tiles.

Also:
* Remove old classes.
* Change height of tiles.
* Add back clipping on PagedTileLayout, as the views don't need to go
outside its bounds.
* Fix a scrolling issue

Fixes: 187460996
Fixes: 187966021
Fixes: 187334034
Fixes: 188459321
Test: manual
Change-Id: Ide520f26982a3f2c8918424cb4c14d3d14da3724