Stabilize standards for SCS-compatible IaaS v5

[mbuechse]

See #787 for list of standards -- go before Team IaaS with the respective PRs:

• scs-0114-v1: Stabilize volume type standard #808
• scs-0115-v1: Stabilize standard regarding default rules for security groups #809
• scs-0116-v1: Stabilize standard regarding key manager #810
• scs-0117-v1: Stabilize Volume Backup Functionality standard #752
• scs-0121-v1: Stabilize standard regarding availability zones #811
• scs-0302-v1: Stabilize Domain Manager Role Standard #586

While we are at it, also make sure to approve

• Harmonize titles between main documents and supplements #812

[anjastrunk]

All tasks are done. I guess, we can close this issue. @mbuechse What do you think?

[mbuechse]

Yes, this is done.