Improvements to the documentation

User

Getting Started:

• Installation

Applications

• Designer
• GUI builder
• scripting / cli interface + Auto updates
• (pre-built GUIs, e.g. alignment GUI)
• Video Tutorials

Widgets

• everything that is accessible from within Designer
• follow https://material.angular.io/components/categories

Developer

• Single-responsibility concept (Widgets only display)
• BECDispatcher
  • callbacks
  • accessing the client
• How to develop a new widget
  • Recommended inheritance (BECWidget, BECConnector)
  • cleanup
  • tests; how to write unit tests with qtbot; e2e tests