Move all unit tests into the appropriate src/test/java/

This trick was performed by

	for java in $(git grep -l junit src-plugins/*/src/main/java/*)
	do
		target=$(echo $java | sed 's|src/main/java|src/test/java|')
		mkdir -p ${target%/*}
		git mv $java $target
	done

Noticed by Albert Cardona.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>