Add some utilities (possibly dispensible commit)
Delete pvectorize.R (superseded by bpvectorize)
Add bpmvec, with default implementation

Still need param-specific optimized methods
Fix bpmvec
Add TODO item
Small tweaks in bpvec
New multi-arg capable bpvectorize
Fix bpvectorize
Add test for multi-arg bpvectorize
Change bpvectorize default to only parallelize first arg
Rename bpvectorize VECTORIZE.ARGS to VECTOR.ARGS

This is more accurate since we are not vectorizing the args in
question, we are parallelizing args that are already vectorized.
Fix arg name in AllGenerics.R
Code tweaks and small fixes
Update documentation to fit new code