TODO: Check out options for freqtable data structure.
      Things to try out: fmindex/afi, hashtable, accumArray, HsJudy
      And perhaps combining key and count into an Int(|eger|64)?

----------------------------------------

TODO: support shaped keys
TODO: Repeat ID:
	output report (.tbl, .out)
	* calculate 1..k'th order entropy
	* other?

TODO: Mask against library

TODO: three-pass: build FT, build library, mask against it

TODO: calculate distrib and mask over windows (w=200? 400?)
   avoids different treatment of different length sequences

- Clustering

- Clustering with (SG/Lee) assembly

 -> statistics to use when clustering:
    1. mode of word counts distribution (= coverage)
    2. estimated p value (1-var/mu) (= avg. overlap)