Several fixes and changes

* Added interactive debugging
* Better exception logging
* More tests for errors
* Added ONBUILD to dockerfile
  Now creating new images based on senpy's is as easy as:
  ```from senpy:<version>```. This will automatically mount the code to
  /senpy-plugins and install all dependencies
* Added /data as a VOLUME
* Added `--use-wheel` to pip install both on the image and in the
  auto-install function.
* Closes #9

Break compatibilitity:

* Removed ability to (de)activate plugins through the web

senpy/schemas/error.json

@@ -13,7 +13,7 @@
           "type": "list",
           "items": {"type": "object"}
         },
-        "code": {
+        "status": {
           "type": "int"
         },
         "required": ["message"]