* Slide the password fields down whenever they are shown.
* Add slideUp/slideDown, fadeIn/fadeOut to dom-jquery.js

* Remove the signup page and all remnants of it.

* If the user types in a known secondary, redirect the user to the signin page.
* If the user manually clicks the "new to persona?" or "Existing account?" links, clear the stored email address.

* If the user enters an unknown secondary email, redirect them to the /signup page.
* If the user arrives with a known secondary email in storage, show the password field.

fixes #2116

improve i18n of main site - strings for translators should not include site implementation details (links, ids, etc) - this prevents accidental breakage and allows us to change our ids and links without requiring retranslation.  closes #2093

Rather than going straight to the quick setup, we should link to somewhere that
gives a little more context.

'or' was not gettext() decorated in index.ejs - allow a translator more control over the whole phrase

gettextify the last portion of the about page.

Cachify the logo as well.

issue #1999

extensive testing of i18n mechanism - including english fallback, string substition from .json files, and debug locale

* in each top level layout or ejs template, include a link to a partial that contains the license.
* The bottom of the license contains a link to the repo and the current SHA's commit.

issue #1167

rename the 'add email' email we send out to 'confirm', and use it in both the email addition case, and the email reverification case.  This is more about semantics than behavior change

Generalize error-display to extended-info.  For every "screen" that is shown, create an extendedInfo and instantiate it.  Remove the "error-display.show" code that was in page_helpers and page_module.

issue #1916

issue #1938

issue #1941

issue #1871
issue #1937

* Add a new module called dom-helpers with function makeEqualWidth.
* Force buttons on the "Is this your computer" screen to be the same width.
* Update CSS enable button width to be set this way.
* Update CSS to vertically center helper text.
* Update CSS to make the buttons look good in mobile.

issue #1932

issue #1925

Change the placeholder for the verification password from "Repeat Password" to "Verify Password" to match the dialog.

issue #1923

issue #1895

Make the options passsed to the check_registration controller more explicit.  Uncollapse the signIn divs in dialog.ejs  Fix string extraction.

fixes #1861