Thanks to @simonft for all the help.

- Resolves: #8980

Defaults to True. Without it, the confirmation modal doesn't show and
you aren't able to remove a provider from the list.

As a couple of initial, example tests, Center and Confirmation were
refactored and tests were set up and added with mocha, enzyme and
chai. Spinner was also refactored.

Previously, if the active VPN was in the connecting state and the VPN
status component for another account was rendered the status for the
new account would show as connecting. This was because it didn't check
the domain returned from the status endpoint when parsing the returned
data and setting "connecting" as the status. We can safely assume that
a non active VPN is in the "down" state, so that's what this commit
does.

The version of webkit we're using doesn't understand display: flex,
instead it needs display: -webkit-flex.

This adds a lock icon to the account list next to the account with the
currently active VPN. The icon is green if the VPN is connected,
yellow if the VPN is connectiong, and red in any other case.

- Resolves: #8853

When filling out the signup or login pages, and when adding an
additional service provider, the enter key will trigger the submit
action. When on the choose provider page, enter will take you to the
next page.

- Resolves: #8841