Fixed MAC related bug with ClassLoader

on mac the contextclassloader gets overriden due to a 1.7 bug in Java.
Therefore we have to set our own class loader in the SciJava Context.
Merge branch 'master' into 0.9

Conflicts:
	org.knime.knip.imagej2.core/src/org/knime/knip/imagej2/core/IJGateway.java