move image_rotate.cpp to nodelet directory according to the directory convenstion of image_pipeline
make image_rotate nodelet class
add executable to load image_rotate/image_rotate nodelet.
add xml file to export nodelet definition.
use getNodeHandle rather than getPrivateNodeHandle
use NODELET_** macros instead of ROS_** macros
Merge pull request #62 from garaemon/image-rotate-nodelet

Image rotate nodelet