Merge pull request #1914 from mozilla/issue-1902-bounce-email-screens

fix(confirm): redirect to signup on bounced email error

r=@shane-tomlinson
fix(client): Go to the /cookies_disabled screen instead of the /500 screen if cookies are disabled.

The User model was accessing localStorage directly which causes most browsers to except. If localStorage is disabled, create a Storage object with a NullStorage backing instead.

fixes #1919
Merge pull request #1920 from mozilla/issue-1919-cookies-disabled-explosion

fix(client): Go to the /cookies_disabled screen instead of the /500 screen if cookies are disabled.
chore(changelog): manually update changelog for 0.26.2