Initial glossary (#3568)

* Initial glossary

* Allow markdown in the description

source/_docs/glossary.markdown

@@ -0,0 +1,20 @@
+---
+layout: page
+title: "Glossary"
+description: "Home Assistant's Glossary."
+date: 2017-10-08 08:30
+sidebar: true
+comments: false
+sharing: true
+footer: true
+---
+
+{% assign entries = site.data.glossary | sort: 'topic'  %}
+
+<ul>
+{% for entry in entries %}
+  <li>
+      <b>{{ entry.topic }}</b>: {{ entry.description | markdownify }}
+  </li>
+{% endfor %}
+</ul>