[system_monitor] dockyard lib

This adds code for the Dockyard library. Right now the only API just adds two
integers together. This is like a 'hello world' program for the GUI to call into
as a test. This API will then expand to allow the GUI to query the Dockyard for
Sample data.

Test: run system_monitor_tests executable.

Change-Id: Iee7340d10584d172d39665806f3fbb2e21888e77