Make handling of MEF files easier

Though an example of working with MEF files was added to the documentation in #694, we should make it easier to work with these files given the growing number of mosaicked cameras.

Start by reviewing the MEF example added to the documentation in issue #694 and the current handling of MEF files. The issue does not identify files, tests, or a specific workflow to change; first clarify what easier handling should mean for mosaicked cameras. Done would require an agreed scope and corresponding tests or documentation.

Written by the indexing model from the issue text.