Feature/mkdocs with versioning (#333)

* docs: restructuring & introduction of mkdocs with versioning provided by mike

* docs: ad repositories section to sophia examples

* docs: refactoring and consistent naming of æternity

* docs: hint for new file destination

* docs: revert capital letter

* docs: accept proposed changes

* docs: fix anchors in stdlib

.docssite/overrides/main.html

@@ -0,0 +1,8 @@
+{% extends "base.html" %}
+
+{% block outdated %}
+  You're not viewing the latest version.
+  <a href="{{ '../' ~ base_url }}">
+    <strong>Click here to go to latest.</strong>
+  </a>
+{% endblock %}