unit with suffix has displayable of none

[huss]

Describe the bug

If a unit has a suffix then its displayable should be none. Currently unit create and edit do not enforce this. This shows it does force the type of unit but not the displayable:

Expected behavior

Meter do something similar as seen in:

and units should warn and set to none.

Additional context

None

[danielshid]

I will be working on this issue.