Enhance to deal with many catalogs

[dylanmcreynolds]

Currently, the Databroker Catalog Viewer attempts to open all catalogs that databroker can provide via
databroker.catalog

This presents several issues. First, at NSLS-II, beamlines get a single common configuration setup that includes many beamlines that cannot generally be accessed from each other. So, Xi-Cam opens and touches each catalog to create a list, databroker waits 30 seconds for an underlying mongo timeout. This is done serially, so it could take half an hour to present catalogs. We don't necessarily need to touch each catalog, except that we want to be able support nested catalogs (e.g. a catalog that is an intake server will contain catalogs) we want to flatten the list to contain those children, so to lightly display catalogs just by name would require a more complicated name to catalog mapping than we want to employ.

We have talked a lot about what the implementation should really be. We want to cover multiple use cases like:

1. A beamline machine is configured which for the most part only needs the beamline's specific catalog or catalogs. Rarely at that machines would the user need want to see other catalogs.

2. A user has Xi-Cam installed on their laptop. They may have a relatively small number of commonly-used catalogs, but want the flexibility to reach into any number of catalogs that could be configured on the machine at any time.

This enhancement may include modifying UI for opening catalogs, creating UI and or non-UI mechanisms for creating preferences for commonly-used catalogs.

This is an ongoing discussion with @tacaswell @danielballan @ronpandolfi @ihumphrey