Updating sticky headers.

- The whole section's headers are drawn together, moving as a group
  until it reaches the individual bounds for each letter in the section
- Adding animation to search button -> field transition
- Fixing section header text measuring causing sections not to be centered
- Forcing the merge to stop if an app has > 3 full rows; on both phone and
  tablet, merging a large section with anything else seems to be less useful
5 files changed