Introduce ResourceSets to make loading of resource files more flexible

This MR introduces so called ResourceSets that allow loading Kubernetes manifests either via ConfigMap or from the file system.

Closes #240 (closed)

theodolite/examples/operator/example-benchmark.yaml

@@ -28,8 +28,6 @@ spec:
         replicationFactor: 1
       - name: "theodolite-.*"
         removeOnly: True
-        numPartitions: 0
-        replicationFactor: 0
   appResourceSets:
     - FileSystemResourceSet:
          path: ./../../../../config