Implement /api/v1/zombiereport

[vecna]

A POST cryptographic signed containing number fields:

{
    timestamp: ISO format about when the post is done
    content1: number
    content2: number
}

content has to be defined on tracking-exposed/web-extension#23

from the headers publicKey is associated to an authenticated user, and the number are updated. the number reported are send incrementally. Will never happen that a number sent would be lesser than the previous.

[vecna]

The reason why slave is used despite the historical heritage, is because the interface report back how much time the facebook user spent on facebook. This voluntary contribution is a form of nowadays slavery. but probably using zombie the message remain the same without dealing with the master/slave historical meaning.