Change junit4 bundle dependency so infinitest can be installed in eclipse kepler

The bundle org.junit4 is not available in kepler anymore (see also https://bugs.eclipse.org/bugs/show_bug.cgi?id=402719). Because of this the infinitest eclipse plugin can not be installed in this version. This commit replaces the org.junit4 with a properly versioned org.junit bundle dependency where bundles are available in the eclipse orbit project.