Adapt parser to new schema

see: #121
Now I'm thinking, why exactly did we look-up the `known_user_snps` by `user_id`? When a user uploads multiple genotypes, do we want to not create a new one, when it has already been created when parsing the previous genotype, even though it has that genotype's id? Or do we rather want to have multiple `UserSnp`s with the same name for each of the uploaded genotypes? If I'm not mistaken, they can even have different `local_genotype`s, as the readings are not 100% accurate, right?