As suggested in #263.
* spot/gen/formulas.cc, spot/gen/formulas.hh, bin/genltl.cc: Implement
these options.
* tests/core/genltl.test: Use them.
* NEWS: Mention them.
* bin/genltl.cc: Change the name and add the bibtex entry.
* bin/man/genltl.x: Replace LNCS by LNAI.
* tests/core/genltl.test: Also test the %F output.
Fixes#80.
* bin/genltl.cc: Add --kr-n2, --kr-nlogn and --kr-n.
* bin/man/genltl.x: Add the paper in the documentation.
* tests/core/genltl.test: Test them.