Add CSV file upload

[lkeegan]

• replace single zip file upload with two file uploads: one h5 file, one csv file
• replace /input_file endpoint with /input_h5_file and /input_csv_file
• update model, endpoints and runner accordingly
• validate csv file on frontend
  • parse first line and extract column names
  • require that "barcode", "cdr3", "chain" are present
• resolves #3
• validate file sizes
  • h5 must be less than 50MB
  • csv must be less than 10MB
  • resolves #2
• increase nginx/flask body limit to 100MB