Add schematic dimension images of device to docs

[mariobehling]

For documentation purposes and casing we need schematic drawings a) from top view - Example:

b) from side view with the USB connecting hole - Example:

Please also add images of the drawings to https://docs.google.com/document/d/1ri86SopqFQfGE4EmKPY1KRELkVEmilQp_cFefCcmkak/edit#