Extend Bio-Formats Macro Extensions to extract Channel name,etc.

[bramalingam]

ref: ​https://www.openmicroscopy.org/community/viewtopic.php?f=13&t=7813

[mlinkert]

Might be worth seeing if it makes sense to autogenerate new macro extension methods, so that the macro API more closely matches MetadataRetrieve?. Adding just getChannelName(...) on its own is easy enough, but I'm starting to worry that we're going to wind up with two divergent metadata APIs.

[jamoore]

Splitting due to milestone decoupling.

[mlinkert]

As noted above, my initial long-term thinking for this was to have ​https://github.com/openmicroscopy/bioformats/blob/develop/components/bio-formats-plugins/src/loci/plugins/macro/LociFunctions.java generated by template, just like we do for MetadataStore/MetadataRetrieve?/etc. It may be easier to make a new class that is just the MetadataRetrieve?-wrapping methods generated from a template, and update LociFunctions? to extend that and keep all of the non-MetadataRetrieve?-wrapping methods (so LociFunctions? remains the class to update when something needs to be deprecated or otherwise maintained for backwards compatibility). If anyone has a better idea, feel free to explore that instead, but it seems best to avoid adding a few new methods here and there whenever we get a request.

Possibly ties in with ​https://trello.com/c/c3H2HYzm/51-add-more-well-commented-examples for documenting new macro functions.