fix(client): Do not fail on startup if cookies or access to dom.storage is disabled.

* Work with the author of crosstab to ensure it works as expected with cookies and localStorage disabled.
* Ensure the /cookies_disabled page renders if the user reloads it while cookies are disabled.

fixes #1848
fix(client): The FxDesktop broker no longer sends the `session_status` message on startup.

The call to `session_status` was originally used to determine which page the content server should start at. Firefox now opens content server with the correct page, so this call is no longer necessary.

`session_status` can cause problems. After a logout from Sync, the content server redirects to /signin and Firefox no longer expects a `session_status` message. A channel timeout occurs, and the user is immediately redirected to /500.html.

Bump the channel's DEFAULT_SEND_TIMEOUT_LENGTH_MS to 5000ms

fixes #1883
issue #1830
fix(client): Autofocus on /signup works again.

PR #1855(Handle bounced emails) introduced a regression that eliminated autofocus on the /signup page unless there was a bounced email.

fixes #1891
Merge pull request #1866 from mozilla/issue-1848-localstorage-disabled

fix(client): Do not fail on startup if cookies or access to dom.storage is disabled.
Merge pull request #1893 from mozilla/issue-1891-signup-focus

fix(client): Autofocus on /signup works again.
Merge pull request #1885 from mozilla/issue-1883-no-session-status

fix(client): The FxDesktop broker no longer sends the `session_status` message on startup.
fix(client): The Sync flow should not notify the browser of login after the signup confirmation poll completes.

The browser polls in the background for the status of the sign up completion itself, the client does not need to notify it of completion.

In addition, the /confirm screen should not transition to the /signup_complete screen, this causes a jerky UI.

fixes #1881
fix(client): Notify Sync of unverified logins and signups before the user verifies her email (regression fix)
Fix the jshint error, add unit tests for beforeSignUpConfirmationPoll
Fix the failing 'choose option to customize sync' functional test.

The test was failing because it was not listening for FxA commands and the channel was timing out when sending the `login` message in FxDesktopBroker's `beforeSignUpConfirmationPoll`

Test is moved to sync_sign_up.js where the rest of the Sync tests live.