Improve item visual separation in full(er) log view.

- Add shading to the commit header to make it easier to identify commit
  boundaries in a long list of verbose commit data.
- Disable hover highlighting on verbose commit logs, since that served a
  similar pupose of visual separation.

Change-Id: I0d388d2ccaf9655c612fc2a5e27f229d38d3825f
1 file changed