add pkg-installed signal type and add dbus log

log path: /tmp/dsc-backend.log

tower: https://tower.im/projects/8f19f0bf0e754f0b82ef2c24bc230973/todos/ca23a1b35f564cccac03aaea2e996c91/

Change-Id: Idcdeb84458957208947fa6dc552a85f721c906b7