Feature: Add hierarchy

[gregbaleyy]

Thank you for this very handy tool!

I think it would be very useful to be able to create at least 1 level of hierarchy. In the calculator, we could then have description section to increase readability.
For example, we could imagine something like Paris and London offices with a similar address space. Today, I'm doing something like:

Subnet Address	...	Note	Split/Join
10.100.0.0/24		Paris - DMZ
10.100.1.0/24		Paris - Prod
10.100.2.0/26		Paris - Dev
10.101.0.0/24		London - DMZ
10.100.1.0/26		London - Prod
10.100.1.64/26		London - PreProd

With this feature, the table would become:

Subnet Address	...	Note	Split/Join
10.100.0.0/16		Paris
10.100.0.0/24		DMZ
10.100.1.0/24		Prod
10.100.2.0/26		Dev
10.101.0.0/16		London
10.101.0.0/24		DMZ
10.100.1.0/26		Prod
10.100.1.64/26		PreProd

[Justman100]

@ckabalan