Modified and rearanged documentation files

[Martinius79]

• Modified the root README.MD file heavily
• Added images to be used in the README.MD file
• Created new subfolder "documentation"
• Moved and renamed hardware description folders and other stuff to the documentation folder
• Changed location for images in the MD to the ImagesMD folder in the documentation folder
• Modified README.MD in the pre-build-images subfolder
• Added photos of Elekstube IPS Gen1 and Gen2 and PunkCyber IPS
• Removed hardware modification folder -> Was just one image inside. Moved infos to the end of the README.MD.
• Renamed some existing files in the PunkCyber folder
• Modified _USER_DEFINES - empty - modified the structure of the MQTT section and added inline comments.
• fixed a typo in the TO-DO.txt

Modified the main MD file for more clarity. Added sections, added images, added section numbers, added MQTT section, added Firmware file build explaination, moved sections or modified them.

Modified the MD file in the pre-build-images folder. Added information about the GitHub workflow builds, formated the list of the files as table, modified the feature list.

This is the "Non IPSTUBE" version, just for the existing variants so far.