Keep status of split libraries fastq on the RawData table

We might be able to standardize this, by having state be `(status, log_id)` where `status` is one of `{'not_preprocessed', 'preprocessing', 'success', 'failed'}` and `log_id` is `None` for all cases except `failed`, which has a reference to an actual log id in the `qiita.logging` table (probably the log_id from the job that was doing the preprocessing?)