Only use human names for links when they aren't empty.
Remove redundant platform listing menu item, since Views handles it now.
Do not require a service implementation to load a service type class.

We were only loading service.inc files for service classes, but not for service type classes.
As a result, it wasn't possible for a module to define a service type, without also defining
an implementation of a service. Decoupling these will allows us to (for example) split the
http service type out from the apache service, which in turn will allow nginx-only Aegirs,
which is currently impossible.