svd_eigen_HH: Return error codes instead of assert'ing on error
Modify chainiksolvervel_wdls error processing logic to use solver interface

Provides access to the underlying SVD error code if the SVD computation fails.
vel_wdls: Return data on jacobian singular value conditioning
vel_wdls: Added lambda scaling to wdls chainiksolvervel
tests: Add unit test for WDLS solver
Merge branch 'fix-wdls-solver-error-logic' of https://github.com/snrkiwi/orocos-kdl into fix-wdls-solver-error-logic