Service Type Framework refactoring

Service Type Framework refactoring

implements blueprint service-type-framework-cleanup

* Defines logic and API for ServiceProvider - read-only entity
that admins provide in configuration and which is stored in memory
* ServiceType entity which maps to ServiceOfferings in new terms
is removed for now.
* Routed service insertion fixed to not to refer to service providers.
* In case configuration changes and some service providers are removed
then the resources must be cleanup in a special way (undeploy logical
resources). This is a matter of future work
* Add migration.

Change-Id: I400ad8f544ec8bdc7d2efb597c995f284ff05829