Feature/sample sheet support

[pavlemarinkovic]

• Added support for autogenerating sample sheet function(s) for Nextflow app wrapper.
• sbpack will now avoid overwriting previous version of sb_nextflow_schema.yaml
• Enums will be better parsed and generated
• New --auto mode tries to locate as many files and inputs for generating the app automatically
• The logic for uploading the app code package and the app itself has been updated. It now first tires to create the app wrapper, and if it succeeds then tries to upload the code package.