implement scheduler

- scan for apps every 10 minutes and schedules tasks
- uses docker.exec
    - there is no way to control exec container. docker developers
      feel exec is for debugging purposes primarily
- future version will be based on docker run instead

part of #519

package.json

@@ -16,7 +16,7 @@
     "async": "^1.2.1",
     "aws-sdk": "^2.1.46",
     "body-parser": "^1.13.1",
-    "cloudron-manifestformat": "^1.9.1",
+    "cloudron-manifestformat": "^2.0.0",
     "connect-ensure-login": "^0.1.1",
     "connect-lastmile": "0.0.13",
     "connect-timeout": "^1.5.0",