Instructions for setting up the dev environment - from scratch

WIP. Expected additions later
Minor stylistic changes
Teacher now get two options for worksheet compilation ...

Worksheets can either be:
  1. Homework, in which case students get their own PDFs in their own accounts OR
  2. Classwork, in which case a composite PDF is generated which the teacher
     must print out and later scan

Old code for setting deadline and durations is being retained - though not
being used. Might come in handy later