Added new config files and a missing `__init__.py`

Also moved location of a variable in `default.yml`

buildgrid/_app/settings/cas.yml

+server:
+  port: 50052
+  insecure-mode: true
+  tls-server-key: null
+  tls-server-cert: null
+  tls-client-certs: null
+
+description: |
+  Just a CAS.
+
+instances:
+  - name: main
+    description: |
+      The main server
+
+    storages:
+        - !disk-storage &main-storage
+          path: ~/cas/
+
+    services:
+      - !cas
+        storage: *main-storage

buildgrid/_app/settings/default.yml

 server:
   port: 50051
+  insecure-mode: true
   tls-server-key: null
   tls-server-cert: null
   tls-client-certs: null
-  insecure-mode: true
 
 description: |
   A single default instance

buildgrid/_app/settings/remote-storage.yml

+server:
+  port: 50051
+  insecure-mode: false
+  tls-server-key: null
+  tls-server-cert: null
+  tls-client-certs: null
+
+
+description: |
+  A single default instance with remote storage.
+
+instances:
+  - name: main
+    description: |
+      The main server
+
+    storages:
+        - !remote-storage &main-storage
+          url: "https://localhost:50052"
+          credentials:
+            tls-client-key: null
+            tls-client-cert: null
+            tls-server-cert: null
+
+    services:
+      - !action-cache &main-action
+        storage: *main-storage
+        max_cached_refs: 256
+        allow_updates: true
+
+      - !execution
+        storage: *main-storage
+        action_cache: *main-action
+
+      - !cas
+        storage: *main-storage
+
+      - !bytestream
+        storage: *main-storage