WIP: (PDB-950) Added upfront validation for regexps in queries in API v4 for HSQLDB

This comes from [PR-1142](https://github.com/puppetlabs/puppetdb/pull/1142) to simplify merge/discussion.

This PR adds a simple validation for regexps in queries in all APIs v4.
It validates regexps using Java rules, so there might be some constructions that pass this validation but won't be valid in Postgres.
Here is an example of such construction:
curl -v 'http://localhost:8080/v4/fact-contents?query=\["~","name","\\p\{Alnum\}"\]'

Those regexp differences are discussed in original [PR-1142](https://github.com/puppetlabs/puppetdb/pull/1142).
Or better yet, create a `hsqldb?` function in `storage_utils.clj` much like how `postgres?` works. That will abstract away the lookup, and I can presume we'll use such a function again.