User and AjaxView improvements, new password field

Added more string resources for user and ajaxview output
AjaxTransformedStringView now accepts an additionalError as a
Ref[String] - when there is no input error and this is non-empty, it is
displayed as an error alongside the input box. Input errors are still
automatically generated when the user provides string input that cannot
even be parsed by toT function, since this is the most immediate error.
This permits for example validation of a "repeat password" field, which
needs to use the state of other boxes to produce the error.
Also added optional ElemAttr varargs for the text field, to allow for
password fields with type="password"
Simplified password validation in User, and moved strings to properties.
UserResetPassword has been replaced with UserReset, and the old
UserResetPassword removed.
UserSignup now rechecks all data before trying to create a user, and
also catches exception when email already exists in database. Now uses
new AjaxPasswordView and AjaxPasswordRepeatView