Integration tests and test utilities

Created by: dbluhm

After some discussion with @jayjaybillings on the best approach to testing our Persistence Handlers, it became clear we needed integration tests for them. This PR implements those integration tests.

To have these tests run at a later stage from unit tests, I created a new package for them. Additionally, as these integration tests will have environment prerequisites and it would probably be annoying to have them nested alongside the unit tests if you don't have everything set up, I opted to place it in a new top-level project org.eclipse.ice.tests.integration. We can use this package for any other needed integration tests.

CC: @osbornjd