Adjusted some Heavy tests
merge error
killed warning
killed warning
Added tests for minkowski with only one child
Merge branch 'master' into issue527

Conflicts:
	tests/regression/cgalpngtest/minkowski2-tests-expected.png
	tests/regression/opencsgtest/minkowski2-tests-expected.png
	tests/regression/throwntogethertest/minkowski2-tests-expected.png
minor clarification
Added test of minkowski2 with >2 children
Merge branch 'master' into issue527
bugfix: 2D minkowski was slightly broken; only one child and >2 children didn't work correctly