Sdf change log


 * 1) SDFormat 1.4


 * 1) SDFormat 1.4.8 (2013-09-06)
 * Fix inertia transformations when reducing fixed joints in URDF
 * Add  element to support terrain paging in gazebo
 * Further reduce console output when using URDF models ,


 * 1) SDFormat 1.4.7 (2013-08-22)
 * Direct console messages to std_err


 * 1) SDFormat 1.4.6 (2013-08-20)
 * Add tags for GPS sensor and sensor noise
 * Add tags for wireless transmitter/receiver models
 * Add tags for playback of audio files in Gazebo
 * Add tags for simbody physics parameters
 * Log messages to a file, reduce console output
 * Generalize ode's  element
 * Various bug, style and test fixes


 * 1) SDFormat 1.4.5 (2013-07-23)
 * Deprecated Gazebo's internal SDF code
 * Use templatized Get functions for retrieving values from SDF files
 * Removed dependency on ROS