Tests for the trix tool, minor refactoring on it.

trix_process_entry was extracted from trix_process, tests for
trix_probe, trix_parsevar and trix dispatch calls were added
Extracted reporting modes for lib/posit.sh

Functions for reporting modes were extracted from lib/posit.sh
to lib/posit/cov.sh, lib/posit/spec.sh and lib/posit/tiny.sh