Config finder hotfix

[thebioengineer]

identified a bug in the original logic when:

• validation.yml exists in working dir
• validation.yml has been copied into output dir

then trying to rerun validation code, it isnt sure which to pick.

Code now has a "config_selector" function that selects:

• if interactive, selects the one in the working dir.
• if not interative, selects one closest to current dir (ie if knitting rmd, will select closest validation.yml (assumes in child folder))

[thebioengineer]

Good point @mariev - added in the latest commit!