Bug 1030352 - Delete/undo-delete phone number button in edit dialog does...

... not have an accessibility label
Need to add localization comments for all string that are for screen reader. See examples:
* for multiple strings: https://github.com/mozilla-b2g/gaia/blob/master/apps/ftu/locales/ftu.en-US.properties#L334-L337
* for one string: https://github.com/mozilla-b2g/gaia/blob/master/apps/ftu/locales/ftu.en-US.properties#L292-L294