Isolate backend / frontend / data mocker

[andresenwc]

Reorganize the code structure into subdirectories. In particular, have specific and separate subdirectories each for:

• The React frontend
• The Flask backend
• The data mocker
  • Remove the packages specific to the data mocker from the frontend's package.json
    • faker, lodash.samplesize, mysql2
  • Create a package.json specifically for the data mocker and convert relevant requires to imports