Make filter (on OpticalChannel and LightSource) an optional Device

[CodyCBakerPhD]

I've wanted/needed to add filter information for optical channels several times in the past

This has always been using the free-text aspect of that field, so quite unstructured, but it's always included the following patterns

name of the filter
description of extra details mentioned in the methods section
manufacturer, often Semrock but I can only assume they aren't the only company that creates such things

As such, I think it would be much more efficient to specify a filter as an instance of a device - but still only optional - if anyone does want to attach it to their microscopy metadata