cashew: gmock integration

Separate interfaces from impls to support creation of mock
ServiceManager, Service, and Device objects.
Integrate gmock (Google C++ Mocking Framework).
Remove glib integration from public interfaces.

BUG=chromium-os:7775
TEST=unit tests (FEATURES=test emerge-<board> cashew)

Change-Id: I46156233836468d319710e578e9a08427964b7eb

Review URL: http://codereview.chromium.org/6395007
19 files changed