Added Apple specific meta tag

This meta tag leads to a real full screen app.
See https://developer.apple.com/library/content/documentation/AppleApplications/Reference/SafariHTMLRef/Articles/MetaTags.html

templates/index.html

@@ -1,6 +1,11 @@
 {% extends "layout.html" %}
 {% import "bootstrap/wtf.html" as wtf %}
 
+{%- block metas %}
+{{super()}}
+<meta name="apple-mobile-web-app-capable" content="yes">
+{%- endblock metas %}
+
 {% block content %}
 <h1 class="text-center">Binary Kitchen Doorlock</h1>
 <div class="row">