implement --low and --high parameters for rank, ldcalc,etc.

[kosloot]

indexer(NT) has --low an --high parameters:
--low=<low> skip entries from the anagram file shorter than 'low' characters. (default = 5) --high=<high> skip entries from the anagram file longer than 'high' characters. (default=35)

we (might) need this for the other tools too. In LDcalc for sure.
other tools to investigate

[kosloot]

ok. some more details are needed.
For LDcalc, I assume the --low and --high options are to be imposed on the words from the 'clean' file?
With the same default as used in indexer(NT)?

And for other tools? @martinreynaert please clarify.