Add a sql database for running app locally

[aanchan]

WWW As a developer working with this project, I would like dependencies to be as local as possible From https://github.com/SlangLab-NU/VoiceCollector/issues/1 it would be apparent that db_helper.py needs a database hosted in the AWS cloud to keep track of file metadata.

AC:

• Make database connection variables configurables
• As a first step create tables in Python in an in-memory database like sqlite
  • https://pythonbasics.org/flask-sqlite/
  • https://www.digitalocean.com/community/tutorials/how-to-use-an-sqlite-database-in-a-flask-application
• Have the app run locally with unit tests in place if necessary