Extract the web api code to an independent package

[arbulu89]

Right now, the web api code belongs to the web package. In order to have a more structured code, we could extract this logic to an additional package, which would have its own json models, etc

This is not an easy work, as the golang package structure is not an easy thing, Specially, because you need to avoid the cyclical import inferno, which is a pretty normal thing if you don't abstract all of your models and entities properly.