changed type signature on AbstractVectorStream to remove unecessary extra type arg
experiments with vector joins with a key mapping function
experiments with ideas for nested vectors (i.e. composite keys), motivated by how I'd vector-wise compute difference in per-product AccVol for multiple different feeds (without having to do a manual subset/join for each feed)
Merge remote-tracking branch 'origin/master'

Conflicts:
	src/scespet/util/package.scala
Testing a new vector join that allows key mapping while joining. This supports usecase of comparing Reuters versions of a feed against other providers for each product.
Bug fix in vector.subset
more tests