Executor API Re-Design

[troeger]

The Executor API is a mess. The re-design should focus on the following aspects:

• Use some API framework for the web server site that is not tied too much to the model, such as Tastypie. Django REST Framework is overkill.
• Offer direct API calls for storing performance information, even 'on-the-fly', so that we get rid of the command-line argument to the validator script.
• Let both the validator library and the executor daemon use the API consistently.
• Shift to some 2015 authentication scheme for executors, such as OAuth.
• Consider usage of the API for frontend JS stuff, such as self-updating job status indicators.

[Feinbube]

Sounds awesome :)