Add support for entity class operation annotations

[toby-griffiths]

I've added the possibility to add the following to a type definition to support operation annotations…

types:
    Person:
        operations:
            item:
                <method>:
                    method: '<method>' # or…
                    router_name: '<route_name>'
                # ...
            collection:
                <method>:
                    method: '<method>' # or…
                    router_name: '<route_name>'
                # ...

This will probably want documenting too, but I'm just squeezing this in to the Hacktober deadline ;o)

[dunglas]

Hi @toby-griffiths, tests have been fixed in master. Could you rebase please?

[toby-griffiths]

@dunglas Have created a fresh PR #144 for the version rebased on the current master.