Add helper message for option -c about single-quoting the combo to avoid the shell interpreter to substitute the variables
Add function to count the number of digits (in base 10 or other)
Implement Karou's suggestion for multiple combo in eval-table

If multiple combos are given (by files or command line), then the
output will be by default split into several files, one for each
combo.
Merge remote-tracking branch 'refs/remotes/origin/master' into eval_table_improvements
Merge pull request #140 from opencog/eval_table_improvements

Eval table improvements