Release v1.5.7.3

This patch release fixes three minor bugs, some of which were accidentally introduced with the big changes in v1.5.7.0.

1. Fixed a bug in the .janno reading triggered by trailing à characters.
2. Reverted unspecified behaviour: 0 is again allowed in the Nr_SNPs .janno column.
3. Fixed a bug introduced in v1.5.5.0, where command line input using the -p option would not behave correctly if the input files have multiple file endings, separated by dots.