Make plugin Production-safe

[NickGreen]

We should make the plugin production-safe:

• It may end up on a production site accidentally
• We may want to intentionally keep it on a production site, so that a partner can create development site(s) from it and have it be safe.

Action items:

• Create utility function that checks if the site is development site
• Add a call to that function in the auto-run function
• Add a call to that function on the tools page, conditionally disabling the buttons and adding some language about it being a production site and how to set the constant
• Add a call to that function in each of the actual functions that do things (so someone doesn't somehow trigger them manually)
• Add a call to that function to conditionally not display the admin notice

[NickGreen]

First pass here: https://github.com/a8cteam51/safety-net/tree/feature/protect_production_sites

[NickGreen]

Closed here: #45