Create toggles for create_steps in BP_Group_Extension

[boonebgorges]

It can get a bit overwhelming when you have a bunch of BP_Group_Extension plugins that add steps to the group creation process. Creating a simple group can take 7, 8, 9 steps. I had a brainstorm that we might rethink this process a bit, by adding (maybe to the first or second step of the process, which are BP core steps) a set of "Group Extras" checkboxes. These would allow the group creator to select which additional setup steps should be shown subsequently. Eg,

Group Extras
_ Docs
_ Group Blog
_ Send Invites
_ Avatar

Only those that are checked will have their creation steps enabled.

I could implement this as a plugin first, but I wanted to gauge others' thoughts about usability. Thanks.

[r-a-y]

This sounds related to imath's group management work in #2673.

I'm going to mark this ticket as a duplicate in favor of that ticket.