Added kdl_arm_kinematics package

It is basically a fork of arm_kinematics with many many fixes. It adds a
service call to set the task space and joint space weights used by the
IK solver.
Added lambda value
Implemented service to get weighted IK

It basically uses the KDL::ChainIkSolverVel_wdls class to solve IK. The
service takes weight matrices and the lambda value, the pose, a tool and
the seed state of the robot.
Weighted IK service is working
Initialize lambda with a non-zero value
Some more logging in IK

Output number of iterations and warn when getting a NaN during IK calculation.
Reduce default number of iterations to 100
Extended kinematic chain to also include the spine
Added launch file for left arm
Made default KDL weights and lambda value configurable via ros params
Set better default values for IK solver in launch file
Added launch files for KDL based IK on the PR2
Set output to "screen" for kdl ik services
Fixes to cram_physics to make it work in electric
Set link_names to ik solver info service.
Fixed compilation problem by accessing an enum ideomatically.
Explicitly included `urdf/model.h' because it is not included implicitly anymore
Extracted package kdl_arm_kinematics from cram_physics.
Merge branch 'master' of ../cram_physics
Removed duplicated files.