Split up com.codeaffine.test.util

[rherrmann]

Because of the RepositoryHelper, test utility bundle now has a Require-Bundle dependency on o.e.core.runtime. Some time earlier, the DisplayHelper brought in (unversioned) package imports to SWT.

These legacy dependencies (in particular core.runtime) might hinder using the test utility in other places, where there is no Equinox (or even OSGi?) or no SWT available. Therefore I was thinking to extract those test helpers into a bundle of their own.