Added JDBC event store

Added a pure JDBC implementation of event store that allows tests to be run using an in-memory DB in milliseconds instead of seconds; avoiding enterprise-level bloat :)

There is a certain amount of duplication of the existing JPA code in the new "jdbc" structure, especially in the "criteria" submodule, where the lack of named parameters is the primary difference between pure JDBC and JPA.

It would be possibly to extract some of this code into a "shared" module of sorts, but since there is also some value to keeping these modules disjoint, I think your input on this would be nice. Currently there are a few classes from the "jpa" package being use in the "jdbc" package because they could go entirely unchanged.

For usage sample see org.axonframework.eventstore.jdbc.JdbcEventStoreTest