Resources support (#63)

* Resources support

* Ability to provide VM and worker resources via the CLI

* orchard dev: always listen on :6120

* orchard dev: support --resources

* REST API: provide resource defaults when creating VM

* OpenAPI: document "resources" field

* orchard dev: serve Swagger API documentation on /v1/

* Integration guide

IntegrationGuide.md

@@ -0,0 +1,16 @@
+# Integrating with Orchard
+
+Orchard has a REST API that follows [OpenAPI specification](https://swagger.io/specification/) and is described in `api/openapi.yaml`.
+
+You can run `orchard dev` locally and navigate to http://127.0.0.1:6120/v1/ for interactive documentation.
+
+![](docs/orchard-api-documentation-browser.png)
+
+## Resource management
+
+Some resources, such as `Worker` and `VM`, have a `resource` field which is a dictionary that maps between resource names and their amounts (amount requested or amount provided, depending on the resource) and is useful for scheduling.
+
+Well-known resources:
+
+* `org.cirruslabs.tart-vms` — number of Tart VM slots available on the machine or requested by the VM
+  * this number is `2` for workers and `1` for VMs by default