'Databaseless' Calcite Client

This is an exemplary command-line client for using the Calcite framework to parse SQL  instructions and queries and hold resulting data structures in memory. The client's capabilities include the creation of tables and views, loading user-defined
functions (scalar UDFs, UDAFs, UDTFs), populating tables, and running queries. The client can in particular toggle between JDBC-proxied and direct Calcite-internal object access according to a defined interface type; although JDBC offers limited insight into the query execution plan.