Working on a rewrite of the ProximityForest code, which is now isolated
in the 'pflite' package.
first pass at parallel building and querying of the forest.
option for forest.getKNearest for the user to indicate a serial or
parallelized query. In some cases the parallel multi-proc overhead
outweighs any performance gains.
first pass at progress indictor for parallel forest building
tweaks
updated forest build progress reporting with the pflite multiproc
version of the proximity forest.