Preprocess: SourceFlags cannot take list

[msilvafe]

Currently the SourceFlags preprocess method cannot take a list of sources and the name that's wrapped into the axis manager cannot be set by the preprocess config file so it's only possible to create masks for a single SSO. We would like to mask all sources in the source list from the CMB maps but at least the moon, Jupiter, and Saturn so we need to update the function according.