Help text + documentation for call tool integration

[vbrown608]

Right now, there aren't a lot of cues to help a non-EFFer understand how to integrate with the call tool. I suggest:

• A page in the repo wiki about adding the call tool API key to your app, finding a call campaign id, and additing it to an action
• Minimal help text on the admin/action settings panel - perhaps when hovering over "Campaign ID", similar to the hover text about photo specs for tweet actions