Removed visible template tags from all theme registration pages

[ajrbyers]

Closes #4272

[joemull]

I think using {% blocktrans trimmed %} and introducing some linebreaks would help a lot with readability here:

<li>{% blocktrans trimmed with password_length=request.press.password_length %}
  Your password should be {{ password_length }} characters long.
{% endblocktrans %}</li>
{% if request.press.password_upper %}
  <li>{% blocktrans trimmed %}
    Your password should contain at least one upper case letter.
  {% endblocktrans %}</li>
{% endif %}
{% if request.press.password_number %}
  <li>{% blocktrans trimmed %}
    Your password should contain at least one number.
  {% endblocktrans %}</li>
{% endif %}

Could we also just move these three blocks to one common template use include?