Update to the documentation - developer guide (dev_guide.rst)

[apos]

Hi,

here goes the first draft of an updated the developer guide to review. I am sure I missed something, feel free to alter, shorten or add things from a development perspective. Just keep me informed.

Some comments:

• Some parts, especially in the “Troubleshooting” section, might find another place somewhere in the user guide (demo mode)
• Probably there are some text-trivia in the development docs from the view of a programming "pro". But making things more transparent by explain a little more than necessary for the "pro" is probably a good way to get people involved ...
• I miss a chapter on the Webserver stack.

I am now off until 30th march due to a business trip, but I will take a look into this.

Cheers Axel

[brickbots]

Thank you so much for this contribution! Developer documentation has been a weak spot for the project and this is a fantastic improvement 🥇