build: General build refactoring

Add vars.mk for variable sharing across makefiles.
Stub and rename example YAML file and template.
  Content to be re-introduced as support is added.
Move generated C++ to a header file.
Add input YAML path option to configure.

Change-Id: Ia06e392e8b120b1e1d8614046064fa432a6f9e18
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/src/main.cpp b/src/main.cpp
index a82bb1d..885d843 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 #include <sdbusplus/bus.hpp>
+#include "generated.hpp"
 #include "monitor.hpp"
 
 int main(void)