Allow QueryDecomposer to decomposer disjunctions with exclusions

So, eg, (this that other -take) can be decomposed to (this -take), (that -take),
(other -take).
Merge remote-tracking branch 'localflax/1.1.x' into topic/aw-parallel
Allow single-valued conjunctions to be decomposed

So +(hello world) can be decomposed to [+hello, +world].
Merge remote-tracking branch 'localflax/1.1.x' into topic/aw-parallel