add a way to search and preview collection information

[pieper]

It would be great to be able to find collections more easily. Currently you need to know what collection you are looking for and you need to find it in the list.

One model that would be nice to follow is the Slicer module selector dialog, where you get a list of available options which then gets subsetted based on what you type in the search bar. It also displays a preview of the documentation for the current selection. It also has checkboxes for whether to search only the name or the full text of the description. This kind of feature could be useful for example when looking for collections with specific modalities or other body parts that are only in the description.

Note that it may be possible to reuse the qSlicerModuleFinderDialog concepts or refactor to use some of the same code, but something simpler is also possible if you want to stick with python.

It's also possible that this feature should be in javascript in the portal, in which case the ability to open in slicer may be enough.