Additional modification of generating hand attached model

Additional modification of https://github.com/start-jsk/rtmros_tutorials/pull/74.
ー modify CMakeList.txt (rosbuild) to generate hand attached models.
ー set ADDITIONAL_ROS_PACKAGE_PATH to find current package, because xacro uses ros package path.
ー change cmake target flag name because it is same with the flag in hrpsys_gazebo_tutorials.