Add user documentation

[StephenNneji]

We need to populate the following pages in the user documentation

• Home
• Installation - add download and installation info for supported OSes
• User Guide
  • overview
  • interface
  • controls window Adds user guide for terminal, plot and controls windows #248
  • plot window Adds user guide for terminal, plot and controls windows #248
  • project window
  • terminal window Adds user guide for terminal, plot and controls windows #248
• Examples - add summary of build-in examples and port Luke tutorial from reflectivity school
• Developer Guide