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