[ENH] Seperating api from all modelling code, to work with new runner

Antonio's models required more flexibility with running models alone rather than with an api, so only the api and concurrent processing facilities are now here.

Removed the namespacing as this had only complicated things in the past, and there is no longer the interconnected modules.

The implementation of the api actually takes place in this repo now (where previously it was implemented in the model repository). Now the config file contains a list of model configs of where to find each model, and a factory function reads this file and then creates an api route for each model config dynamically.