Refactor Configuration File

[svenwltr]

Since we initially designed the configuration, aws-nuke got a lot of new features. These makes the config a bit complicated and I see room for improvement there.

Some ideas:

• the config should get a version field
  • this allows us to convert old configurations to the new format
• drop support for plain string in the filter config and allow objects only (ie having value, property and field) (see Convert All Resources to Support Property Filters #220)
• the filter config should allow to be applied to multiple accounts
  • eg we do deploy the same Terraform code on multiple accounts for staging purposes, and it would make sense to reuse the filters there
• considering to add tag support, we should already design the config in that way (see Question: Only nuke Resources with certain Tag? #218 and Tag Support? #186)