Create proper issues from playground feedbacks

[webhart]

• superclass of 'specific strength'
• superclass of 'unit cell 3D crystal'
• superclass of chemical substance
• Document strategy of inclusion of 3rd party ontologies (current imports required for axioms)
• (Re-) structure devices
• Include more material specific qualities and REs
• Think about inclusion of more objects: pin, disc, screw
• lubricant role