BLOCKER: Allow multiple templates per raw data

Multiple fixes in the PR:
- Allows multiple prep templates per raw data
- Preprocessed data is now linked with prep template rather than raw data
- Fixes #326 
- Changes on initialize.sql:
  - SPECTRA removed
  - SFF added
  - FASTA -> FASTA-Sanger

This PR allows @antgonza to continue with his PR.
Coming in late on this, but @ElDeveloper is right. I was originally thinking of the postgres syntax: `DROP TABLE IF EXISTS table_name`, but the check that @ElDeveloper linked to I think makes even more sense and pushes all the logic into a single query against the db. While this table _should_ exist at this point for dropping, there isn't an explicit guarantee that it does.