allow owner field in app.yaml

[ayys]

• support owner field in app.yaml
• add owner field to app.yaml generated by wasmer app create

makes it so app.yaml can process owner field in two ways,

In descending order of priority:

• via the --owner flag passed to the CLI
• via the owner field in the app.yaml

sample config:

kind: wasmer.io/App.v0
name: my-fun-little-app
owner: <user or namespace> # new owner field
package: wasmer/hello