Continuation of the unified account chooser flow.

 - made the UI match the spec
 - added ability to force the account chooser to appear
 - added ability to pass in a description that will override the stock one
 - added ability to pass in requiredFeatures for addAccount
 - added ability to pass in an authTokenType for addAccount

Bug: 5293377
Change-Id: I243c0fd6598c943b1f65753e1f5d3c86629f64f5
13 files changed