fix(config): relax repo config validation, make rpc work

qri config set over RPC wasn't working properly thanks to an issue with middleware. We've long since moved away from needing repo middleware in favour of different types of repo implementations, so I've just relaxed the requirement that middleware be present & specified.

config/repo.go

@@ -28,11 +28,11 @@ func (cfg Repo) Validate() error {
  "title": "Repo",
  "description": "Config for the qri repository",
  "type": "object",
- "required": ["middleware", "type"],
+ "required": ["type"],
  "properties": {
  "middleware": {
  "description": "Middleware packages that need to be applied to the repo",
- "type": "array",
+ "type": ["array", "null"],
  "items": {
  "type": "string"
  }