Add regression testing to the PL/Java maven build

[thallgren]

We must add junit based regression tests to the Maven build. I think the simplest way to do this is to turn the current examples into JUnit tests and then use the maven-failsafe-plugin to establish an integration test suite that essentially:

1. Drops existing test-database
2. Creates a new test-database
3. Installs PL/Java into the new test-database
4. Installs test functions into the new test-database
5. Runs the JUnit tests

[jcflack]

Believed resolved (or, at least, substantially addressed) in 1.6.0 through Node.class and the CI arrangements; there is now a reasonably convenient way to get the existing tests to run, in a clean test database, and to have that happen routinely.

So I think I can close this.

The need for more tests to be written, of course, continues endlessly. :)