Config update

[LMBradford]

Make or update parameters in the config file, including:

• metadata_file and contrasts_file, so different file names can be used. This will improve organization and documentation on complex projects, where we previously just overwrote metadata.txt and contrasts.txt. Closes issue #233 .
• add bioinformatician_name, so reports will show who ran the analysis
• change project_name to researcher_name, for clarity

Also adds a check that the contrasts file is properly set up, and throws an error if it's not. Closes issue #239

Allows biospyder params to be set to null when running RNA-seq analysis. Closes issue #237 .

[LMBradford]

Tests failing right now because the test data config doesn't meet new requirements.

Still to do:

• change project_name to researcher_name in reports
• add bioinformatician_name to reports
• update config.default.yaml
• allow biospyder_dbs and biospyder_manifest_file to be null in the config schema