Add a box to the Community Creation page to identify community as Sandbox/Demo community

Problem to solve: Our reps have a process to create "Demo" communities for their professors as a way to show a customized example to their professors. We need to distinguish these from "real" communities so that they're not pushed into Salesforce and counted toward our forecasting. Reps are currently instructed to set the Expected Student for these communities at 1 so that we can tell them apart but this is just a hacky workaround.

Potential solution: Create a field or something at the Community Creation page for folks to indicate if this is a "Demo" or "Sandbox" community so that we can use that field to exclude the community when trying to push into Salesforce.
!This box should be available to Packback admins only!