Verify PID-like values in file names when running the applicant file verifier

Attempt to identify values which are intended to be UCAS PIDs in file names, and flag them as erroneous if they're either not valid PIDs or don't match the applicant folder PID. To account for typos, a PID-like value is a sequence of digits (possibly with hyphens) containing 9, 10 or 11 digits, and possibly with a non-digit non-hyphen value someone in it. 9 digit sequences beginning with 2100 are not treated as PIDs as some colleges are using non-PID IDs that fit this pattern.

Remove errors caused by file names with no apparent UCAS PID.

Add a test function to verify the PID-like detector with a range of file names.

Closes uis/devops/digital-admissions/applicant-document-management-service#58