Bug 21311: (follow-up) Adjust wording of failed login message

Bug 21311: (follow-up) Adjust wording of failed login message

Based on the feedback of Jonathan, Katrin, Mark and Martin (thx), adding
the general remark that if lockout is enabled, an account may be locked
out after x attempts. This does not say that the account on hand is
locked or not.

Adding a <p> tag between 'Log in'-button and 'Forgot your password' for
presentation.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit e64650216f568e7d7ad26e25ae59493202d871a3)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>