Support actor aliases for invocation

[autodidaddict]

If an actor has a tag in the form of alias-(alias name) where "alias name" is a URL-friendly alphanumeric string with no whitespace or special characters, then the actor can be referred to globally (within a lattice) by that alias. If two actors with different public keys are started in a lattice, then neither alias will be usable for invocation since the lattice won't be able to disambiguate. In other words, it's up to the developers to ensure the uniqueness of their alias tags.

An alias can be used to allow an actor-to-actor call without having to configure an actor with the 56-character identity of its target. This also helps when the identity of a target changes from development to production because the signing identity of the actor changes as well.

These aliases will make the developer experience of composing actor functionality significantly easier, but are also required to support the OpenFaas capability provider (#99).