FR: Should support variable grouping and group lists

[nembery]

example would be an interface definition that includes multiple fields:

name, ip_address, etc

These fields should be grouped into a dict like:

{"name":"Ethernet1/1", "ip_address":"10.10.10.10"} 

Also, it should then be possible to make a list of such groups so

interfaces = [
  {"name":"Ethernet1/1", "ip_address":"10.10.10.10"},
  {"name":"Ethernet1/2", "ip_address":"10.20.10.20"} 
]

grouped fields should be visually identified somehow, and you should be able to create more of them as desired.