polywrap-core package can be converted to namespace package with sub-packages #113

Refactored polywrap core may look like following:

• invoke
  • invoker
  • invocable
  • invoker-client, etc
• wrap
  • WRAP module
  • WRAP package
  • etc
• uri-resolution
  • Uri-Resolver
  • UriResolutionContext
  • UriResolutionStep
  • UriPackageOrWrapper, etc.
• client-core
  • client
  • client-config, etc