Provide a way to trigger Bellerophon from a regular API call

[ThibaultKlein]

Currently, Bellerophon is good when you call a status endpoint at app start, but doesn't help when every API call can return a JSON triggering kill switch or force update.

We need to provide a way to handle this use case and let the client integrate Bellerophon when API calls are made.

A potential solution is to provide a convenient function to Bellerophon that checks if the force update or kill switch is active, and have Bellerophon return a callback that tells you to show your custom Bellerophon view.

@JamesJSY You've been contributing a lot on this project, is that something you could help with? @Xodia brought up the issue with a project he is currently working on, is that something you could collaborate on?