Make post install pages gracefully handle failure modes

[waltjones]

The currrent install pages call the setup/install routines on a continuous polling loop and do not differentiate between whether a step failed or has not executed yet. (Pending vs. failed.) In the failure case, or timeout, there are no diagnostic hints for the user.

The looping behavior on error conditions can cause floods of emails to the customer's inbox and/or occurrences to the Rollbar account.

Key changes in this update:

• All steps now happen synchronously, except adding the email address, which will be discussed below.
• Completion of each step is verified, and state updated, at the time the step is completed.
• Because adding the email address must be done in a future, the UI will pause at that step for the user to manually advance.
• The UI is updated using a reRender target, and full page loads aren't needed.
• In general, polling and/or refresh loops are no longer needed or used.
• Incorrect tokens (like client tokens) are gracefully handled, returning control to the user with a message.
• Help text to resolve common failure conditions. For now, this focuses on wrong tokens, and insufficient network permissions.