Splitting the single package into a library and a ros node package

I split the monocular_pose_estimator package into a monocular_pose_estimator_lib package which contains a library of the pose estimator as well as a monocular_pose_estimator package which contains a ROS wrapper for the library. Now the library package only depends on Eigen and OpenCV and not on  ROS (This has already been the case before but the files were just packed into one single ROS package).