Changes needed to upgrade to new gradle version

- Add ignore for various lint errors that is introduced in the lint
  update
- Remove GLIF Pixel themes as they are unused and causing lint errors
- Add flavor dimension "compat" as it is now required
- Replace *Compile with *Implementation in the gradle files, as
  needed by the newer Gradle version
- Use build tools 27.0.0 to avoid the Gradle warning
- Use new Robolectric configuration mechanism and removed our old
  hack, per http://robolectric.org/getting-started/

Reference: https://developer.android.com/studio/build/gradle-plugin-3-0-0-migration.html

Test: Existing tests pass
Bug: 70287447
Change-Id: I505476ae3695cd06349766c5e6280299f779f272