Bringing in symmetry with the VectTerm bucketing.
Other cleanups.
Initial unit testing on vector bucketing
Ah, nice new syntax:
stream.bindTo
makes vector binding much nicer.
Not sure there's any parallel for pure MFunc vector construction.
Although.... maybe I can have a further extension of VectTerm that adds "reset" to if we're derived a vector of [K,MFunc]

BucketVect test failing, but I know what to fix now.
New bindTo syntax working on VectTerm
Trying to make 'Agg' special casing simply a Cell that can be auto-bound to a source.
 If we could make 'Agg' just a trait, then any Cell that had the Agg trait could work.
Then we'd build a function holder for an Agg Cell, and Bucket wouldn't need a function holder, because it is one.
initial MFunc vector stream tests working
grouped MFunc vect works too
Getting the MFunc with Bind tests passing now.
I think I've got an idea for a better syntax for this, similar to 'bindTo'
Sweet, that was simple.
bindTo syntax works with complex MFunc/Bucket hybrids
Looking good. Other complex MFunc/Bucket tests work in Vector scenarios with new bind syntax
Initial 'window' test working.
Need to roll out to all other variants