Added removal of NAs from npquantile by suggestion
Replaced ncol(xdat.numeric) with k which is always defined even when
there exist no numeric variables (may require more tweaking in this case)
Trapped glitch when there are no numeric instruments/variables
(nrow(xdat) more robust than nrow(xdat.numeric))
fixed copy/paste bug in np.c which stopped adaptive bws + trees from working properly
Merge branch 'master' into npRmpi