SWIG: fix bugs in SWIG binary checking

- Fail if -version fails in _LALSUITE_CHECK_SWIG_VERSION()
- Use AC_PATH_PROGS_FEATURE_CHECK() to correctly find binaries
- Fail if no binaries are found
Tweak paths in lalinference pp pipeline
LALInferenceProposal: Add ensemble Stretch move (fix #1081)
Affine Walk jump working
LALInferenceNest: Remove PolarizationPhaseJump in favour of
CorrPolarizationPhaseJump
Fix paths in lalinference_pp_pipe