Split libraries fastq

Adds the StudyPreprocesser class, which allows to preprocess the raw data of a study. Currently, it only supports Illumina data, but the code should be easy to expand to support other types.

I've also modified the `insert_filepaths` function, so it now supports to pass the filepath type either by id or by the string (name).

I've modified the initialize.sql file, to support the correct filetypes for the Illumina data and its preprocessed data. I had to modify multiple files due to this change.
I think the only thing not being retained is the split libraries log file, right? At this time, that log file is not easily formatted for subsequent use, but it would be good to retain. 

A single path that is the parent for all PreprocessedData results is not going to scale. I like the idea of specifying somewhere that they can go, but it needs to be flexible such that results can be easily distributed across directories and/or filesystems as to not overburden a specific filesystem. E.g., `/foo/bar/%d/PreprocessedTmp % mod(study_id, 10)`, or something.