Deployments service protos, improved resource name parsing

This adds protos for a currently-unimplemented resource that models deployments of APIs. Clients can be written to call these methods but they will return gRPC UNIMPLEMENTED status codes (for now).

We've also changed the names package in server/registry/names, hiding the regular expressions for resources and recommending use of functions named Parse<ResourceType> and Parse<ResourceType>Collection to validate resource names and extract their components. This is a breaking change for client code that uses the names package.