Built-in JDBC connector alpha

This is a pre-release of the new built-in JDBC implementation tailored for this extension.
The code currently lives in a PR.
Please start a discussion if you encounter any problem with that version.

The best way to read the associated documentation is to generate it from sources (requires Git&Docker):

git clone https://github.com/liquibase/liquibase-neo4j/ --branch liquibase-neo4j-jdbc-alpha-01
cd liquibase-neo4j
./documentation.sh
# browse localhost:8000

Note: this won't be made available on Maven Central, only here