utilities for CoR <=> RoC conversion

...where

  CoR = "column rows"
  RoC = "row columns"

...or, more accurately,

  CoR = "column cellarray of row cellarrays"
  RoC = "row cellarray of column cellarrays"
makedir and openfh utilities
tbl2tsv: initial commit
rename private/nr_.m -> nr.m
enhance nr to quote & escape strings
refactor varnames; add companions
cols2str: stringify table columns
tools to find first difference
table => col of cellstrs
grouped_select.m: WIP
sort_table: a robust sortrows
shufflerows