Add (non-running) examples of plyr options for nblast()
Set NBLAST-with-progress-bar example to run
Add documentation of plyr options for nblast()
Merge branch 'feature/plyr'
Verbatim copies of flycircuit-specific functions
tidy up functions
WIP: function to calculate distances/dotprods

* so far only sets up which pairs of neurons to calculate
Pass vector of distances to NNDistFun

* this should be a completely silent in almost all circumstances
Implement collection of distances/dotprods
bug fix handling missing argument
refactor to simplify mlply call

* named function makes intent clearer