Added -v option to bugreportz.

Calling 'bugreportz -v' will print its version, which will make it
easier for 'adb' to support multiple versions in the future (for
example, next version could display the bugreport progress rather than
wait until it is finished).

BUG: 27653204
Change-Id: I1bbb35a66cfc79ca534ae9eb7c2a53540755d653