Plugin() is confusing because it's not a constructor, it just finds
an existing instance of a plugin object. All other camel-case
functions are constructors in the current lua API.
it makes no sense to specify the type when calling, for instance,
session:lookup_endpoint() or similar functions
it also makes it easier to use iterate or lookup in the object
manager, when we already know the type of the objects that the om
contains
Add the ability to construct an Interest argument without
using the Interest keyword, so instead of:
om:lookup(Interest { type = "session" })
we can now write:
om:lookup { type = "session" }
... and also remove lookup_filtered from ObjectManager
