hope the layers can be ignored by parameter

[CandidXD]

What would you like to be added:
Layers can be ignored by parameter，in the func 'CatalogPackages()'

Why is this needed:
When we scan lots of packages which have the same base layer，we needn't to parse the base layer's packages again and again.

Additional context:
Nothing.

[wagoodman]

I think you are referring to some of the functionality described in #15 , specifically the user / user-squashed scopes. I'm going to close this issue in favor of the original.