Renames `stringLengthCheck` fields

Renames stringLengthCheck arguments minValue and maxValue to minLength and maxLength

Note: This also fixes the version number, previous version was not prefixes with 'v'.

New checks `unique`, `stringLength` and support for `thresholds`

This release adds 2 new checks, and a support for thresholds. Links to documentation are provided below.

• uniqueCheck - Checks that all rows in a set of columns are unique.
• stringLengthCheck - Checks that the length of a string in a column falls within a given range.
• thresholds - Allows a check to fail a threshold number of times before recording it as a failure.

Initial OSS release

Not yet published to a central repository. Must assemble fat jar.