Define new shell commands to get and modify UCE PUBLISH

1) Implement "override-published-caps", which allows a user to add
and remove capabilities from the UCE PUBLISH.
2) Implement "get-last-publish-pidf", which allows a user to get
the last successful PIDF XML or "none" if we are not published.

Bug: 180033898
Test: test commands with "adb shell cmd phone uce ..."
Change-Id: Ifb2125b8f8cf2b85e4efe380ef4b3562abcf3806