Bump parent version to use scijava-common's TestUtils for testing

SciJava common now offers a TestUtils class that has improved versions
of our own createTemporaryDirectory() methods. Let's use them in our
tests, and get rid of our obsolete versions.

To that end, we bump the parent to the pre-emptively deployed
pom-imagej version that already references the ij1-patcher version
we are just about to release.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Use SciJava common's deleteRecursively() and createTemporaryDirectory()

Those versions are better than our own.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Prepare LegacyInjector.preinit() for the upcoming imagej-legacy

The new imagej-legacy version will change the startup, requiring the
PluginClassLoader to be disabled.

The pom-imagej version we use as our parent currently was already
prepared for the new imagej-legacy version, so let's just sneak this
change into the 'test-utils' branch that already bumps the parent.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Merge pull request #18 from imagej/test-utils

Use SciJava common for testing