[jsk_topic_tools] Some fixes following #1446

[wkentaro]

Some fixes are necessary for #1446.

Contains following fixes

• Use project exported library for linking target library

For simplicity and to make it easy to add another configurations for testing.

• Add ::test namespace to avoid conflicts of nodelet class name

If links project exported library, the nodelet class name can conflicts (in the future), so this is necessary.

• Rename to have log_utils in the filename

IMO tests for log_utils.cpp should be log_utils in the filename without any specific reasons.

• Nodelet should be have suffix of _nodelet

This is a standard name rule in ROS, for example:

• https://github.com/jsk-ros-pkg/jsk_recognition/tree/master/jsk_pcl_ros/src
• https://github.com/ros-perception/pointcloud_to_laserscan/blob/indigo-devel/src/pointcloud_to_laserscan_nodelet.cpp