#238 Use optional in junit and hamcrest Maven dependencies

[Viczian Istvan]

DbUnit has junit and hamcrest transitive dependencies.
These dependencies appears in the declaring project
even if I use DbInit not in tests or I use TestNG for example.

Patch: https://github.com/vicziani/dbunit/commit/28ec6acaeaaf1668b1be2e816318ad40d1b55aed.patch

[Jeff Jensen]

Thank you!