improvements to hardware, installation & validation

[orgua]

• hardware
  • add case for observer
  • add test-routine for new capes
  • update testbed information-sticker
  • add cage for cape
  • add bulk holders for up to 5x cape and 10x target PCBs (can be configured via OpenSCAD)
• ansible
  • tweak renaming of hostnames
• correct doc for growing partitions
• herd - add timediff-command
• cal-tool
  • add plotting-script to show multiple cal
  • add CLI-command to plot a cal