This change improves privacy/security by ensuring all local storage (which includes settings, etc.) is destroyed on sign out or when revoking a remote session. Because signing out is now more "risky", the button has been moved to the settings along with other existing sessions.
This commit:
- Removes the power/sign-out icon from the sidebar footer (gives additional room for when the admin panel gets added)
- Adds a "Sign out" button next to the current session info in the settings session list
- Renames "Disconnect" buttons into "Revoke" to better clarify the intent (I will admit that I borrowed the wording from Telegram)
- Fixes incorrect `localStorage.remove` method
- Uses Sinon.js to mock wrappers for `window.localStorage` and `window.location` (does not mock those themselves, in the "Do not mock what you do not own" fashion, mock our layer instead). I expect we will be able to test a bit more from the UI with this. A good next candidate will be the `mockLogger` things.
