* add options to SFSMatrix constructor or solve() method
* finish R data conversion for other input data types
* Update README.md and DESCRIPTION:
  ** how to build until we get into CRAN,
  ** how to read file data
* Update man/*.Rd docs, incl. examples for all input variants
* check CRAN conformance https://cran.r-project.org/web/packages/policies.html
  ** mostly done: devtools::check("../SFS") no longer complains
* submit to CRAN https://cran.r-project.org/submit.html
* check what we need for seriation package