Added initial JDBC implementation. Still missing implementations of UpdatableResource and ResourceProvider.
Added Crud JDBC-based UpdatableResource.

Also renamed some stuff for clarity and eliminated "Statement" abstraction that turned out not to be helpful.
Added Crud JDBC ResourceProviders
Share more async code between Jersey and JDBC Crud implementations
Renamed “adapter” package to more-conventional “util".
Added license to source files
Use try-with-resources