Release v3.15.1

This release fixes mixer integration with the bundle list command
(previously it would try to use the server MoM for the local mix
version).

Swupd search is improved to report real recursive contentsize for bundle
results as a sum of included bundles. Search now displays all results by
default with an optional --top NUM flag to only display NUM results per
bundle. Another flag -m, --csv outputs all results in CSV format so they
can be more easily parsed by a machine.