Pygas

- Make revcomp of reads optional.
- Exact matching only option
- Exact matching speedup

CI test fix: Correct multi-hit test so matches usage on guides being unique regardless of revcomp

Reorganized exact matching code so that matrix match as last resort.

Handle when no rules are specified (no mismatch, ins or del)

Correction to the rule checks

Introduce use of score to allow:

- only best-score alignments to be captured
- matrix generation abandoned as soon as best score cannot be equalled.