[Application][Tizen] Specify session bus address in Tizen

In Tizen the session bus is not available for us by peeking at the
DBUS_SESSION_BUS_ADDRESS, it will be created in a well-known place
instead.

The code change so instead of using the '_for_bus' variants of the
functions, we explicit create the GDBusConnection.

This patch also improves the error message for the case where we fail to
create the object manager client and fix the include rules to follow our
standards.