Allow whitelist and blacklist of namespaces

[ede-n]

Thanks for putting this repository together, we have been using it extensively and came across a use case for which we need to whitelist a few namespaces.

Here I propose to introduce two new arguments

• --include-namespaces: a subset of namespaces to process, if empty processes all namespaces.
• --exclude-namespaces: a subset of namespaces to exclude from processing.
  In this implementation I do not except both the arguments to be provided for the same invocation. If both the arguments are provided, only inclusion list is used for processing, exclusion list is ignored.

I created a PR for the same #104. Thanks.