External packages and example CLI

[masnax]

Depends on #3

This mainly refactors the project to expose some components so that they can be externally called from other packages.
Basically, this moves stuff out of the internal package and adds top-level packages for:

• client - Adds a /1.0 endpoint helper and helpers for querying the entire cluster at once. Creating a client is still internal, except through a few helpers in the microcluster package.
• cluster - The generated components of the database need to be external because external calls to the generator will rely on them.
• rest - Exposes types for API endpoint creation. The actual handling is still internal.
• state - This one's a bit hacky, basically we need the external APIs to have access to the daemon's state to be able to actually do things, so this just exposes a type definition.

Additionally there is now a microcluster package with an App command that takes some state args and interfaces with the internal package to create some useful helpers for interacting with the daemon externally. This will allow passing in our own set of []rest.Endpoint and map[int]schema.Update that will be appended to the /1.0 endpoints and the default schema, respectively.

Lastly there is an example directory with a microd/microctl project inside. This uses microcluster.App along with the packages above to create a basic cluster. Here is the readme.