Threshold output creation

This branch fixes the `createOutput` method of `ComputeThresholdHistogram` implementations to work properly. The issue was that prior to the `imglib2-2.0.0-beta-27` release, there was no way to ask a `Histogram1d` what type of data it had counted. So passing one around lost the type reference. But that is now fixed as of https://github.com/imglib/imglib/commit/d8bed7b61c0de2d83d8510f3c5b5df7f7ed77a1e.