Debug mode for ignore rules

[rcrowley]

Add a debug/verbose mode that prints an explanation of why each file/package/service is or is not included in the blueprint.

[StephenBrown2]

+1

I think it would be useful to have a general debug mode, perhaps with increasing verbosity, to help determine errors and failures so that files that aren't actually needed, esp when creating a blueprint, can be seen and the problem remedied.

(Self-serving plug) This would be particularly useful for #122 and others. /plug