Basic validation

Includes a simple script to perform validation of a mapping file's fields given a directory of controlled vocabularies. Generates a report with the fields that appear to match one or more controlled vocabularies, and lists which fields (if any) have invalid values (i.e., those that do not match against the field's controlled vocabulary). Also performs basic checking for discrepancies in all fields (controlled or not) by checking for differences in capitalization, leading/trailing whitespace, and inner whitespace.

Fixes #5 #6.