Command help message uses help and CLI-Reference generation.
and in convention, help message stops with period ".".
Change-Id: Ia42df8e65aa8ab44f15e28ee0e1753dc17086a48
Improve consistency of help strings - also with other python clients:
* Add missing "." to sentences in shell.py, like the majority already
was.
* Use sentence capitalization for all help strings (compare with
shell.py).
Change-Id: Idb3c5ba5167efc8947b4f2e89ba1b4e3d1863e5e
