feat!: move every layout to demo folder

- source/screens is now free for user files
- rename demo templates to their equivalent sources
- add demo maintenance template
- demo templates use html base element

source/screens/pages/blank.njk

@@ -1,20 +0,0 @@
-<!-- blank.page -->
-{% set pageBase = "../" %}
-{% set pageId = "blank" %}
-{% set pageClass = "h_full_view" %}
-
-{% extends "hippie/_default.njk" %}
-
-{% block title %}Blank{% endblock %}
-
-{% block head %}
-{{ super() }}
-{% endblock %}
-
-{% block body %}
-
-{% endblock %}
-
-{% block script %}
-{{ super() }}
-{% endblock %}