[bug] - samplesheet schema for genome field too strict

[feiloo]

The naming scheme for the "genome" field in the samplesheet is overly strict and forbids using paths containing a slash. It seems sensible to allow more locations than the current directory, like absolute paths.

possible relevant line: https://github.com/nf-core/methylseq/blob/db60bfe1f0d0409244a02c6b046301ebfd697db7/assets/schema_input.json#L34