Add more localized strings

This adds altext on the home icon, copyright is already translated on the footer.html

Fixes #795

sphinx_rtd_theme/layout.html

@@ -116,7 +116,7 @@
           {% if logo and theme_logo_only %}
             <a href="{{ pathto(master_doc) }}">
           {% else %}
-            <a href="{{ pathto(master_doc) }}" class="icon icon-home"> {{ project }}
+            <a href="{{ pathto(master_doc) }}" class="icon icon-home" alt="{{ _("Documentation Home") }}"> {{ project }}
           {% endif %}
 
           {% if logo %}