Add mapper CLI utility

A busctl like CLI that removes the foreknowledge requirement of a
service name by leveraging the object mapper.

Initial applets are call and wait:
 call: Invoke a method
 wait: Wait for a list of objects to appear on the bus

Change-Id: Ic52f09a634949efe8d5c78e51ba965f2e7150018
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
3 files changed