Add a feature flag to expand smartspace to three rows

In order to experiment with presenting more predicted content to the
workspace I have added a flag to expand smartspace to two rows.

This CL does not include any app relocation. If an app lives in a space
the expanded smartspace will occupy, it will be removed from workspace.

Change-Id: I38354dc81a34a495828cf7a69ddb04cc137e2e4e
3 files changed