Move to subproject to enable both projects

Yocto builds need each component to build individually, but meson wants
them to build as a single project. This follows google-misc and moves
to subprojects.

It also enables callback-manager in the build and fixes some build
errors and warnings.

Change-Id: Ie56141bf86b6d9c6b27eb697944fbc392e374c22
Signed-off-by: Jason M. Bills <jason.m.bills@linux.intel.com>
16 files changed