improve configuration help text in auth_token

Related-Bug: 1287301
Change-Id: I3499fdf87b49b7499c525465ccd947edfa5cec6d
Improve help strings

Improve consistency of help strings:
* Add "." at end of help strings and descriptions.
* Improve descriptions.
* Fix capitalization.

Change-Id: I291acea95871734a30192c2e4564267326f9c0a7
Merge "Improve help strings"