I18n/links (#22)

* homepage links

* Link logo to What is Dash page.

* Plugin to generate sitemap.xml

* Link to sitemap plugin github repo.

* Footer links

Still need to create pages for:
* terms-of-use/
* contact/

* Get Dash and Participate links

* New link keys for language yml files.

* Missing Contact and Terms of Use pages (placeholders)

_config.yml

@@ -18,6 +18,8 @@ name: Dash
 url: https://www.dash.org
 description: Digital Cash
 
+url: https://www.dash.org
+
 api: http://www-test.dash.org/api/v1
 
 languages: ["en", "es", "cn", "pt", "ru", "it"]
@@ -32,3 +34,16 @@ collections:
     output: false
   colors: # style guide
     output: false
+
+# https://github.com/kinnetica/jekyll-plugins
+sitemap:
+    file: "/sitemap.xml"
+    exclude:
+        - "/atom.xml"
+        - "/feed.xml"
+        - "/feed/index.xml"
+        - "/style-guide/index.html"
+    include_posts:
+        - "/index.html"
+    change_frequency_name: "change_frequency"
+    priority_name: "priority"