Make service sharing more explicit in policy language

[romangithub1024]

Make it more verbose ("allocation keys" is not verbose enough)

• type = singleton (make it obvious that there is always one instance)
• type = shared + specify scope (make it obvious that same key gets the same instance)
• type = dedicated (make it obvious that every dependency gets its own instance)
  • right now "{{ .Dependency.ID }}" doesn't look too good in the policy