second-stage/programs/wlle: Remove old version of lmdata.c.orig
It's still in revision control history if anyone wants it, but don't see a
reason to keep it around.
Add new reranker retrainer (cvlm-lbfgs)
This is a new Apache license-compatible reranker retrainer. It
uses libLBFGS for optimization and COBYLA to tune regularization
coefficients. This doesn't give exactly the same results as previous
rerankers, but the resulting models appear to be empirically close.
libLBFGS supports both L1 and L2 regularization using OWLQN for the
former.

Minor changes:
- updated READMEs to drop remaining mentions of TAO/PETSc and include install
  instructions for libLBFGS and Boost
- updated Makefile to make cvlm-lbfgs the default optimizer (also made "final"
  the default version since that's presumably what most expect)
- updated wlle Makefile to drop remaining mentions of TAO/PETSc and older
  optimizers which used to use it
- minor improvements to the main README (a task never finished...)