Simplify jinja2 base templates, update theme options

- New realfavicongenerator.net packages (https://realfavicongenerator.net/blog/new-favicon-package-less-is-more/)
- Support all possible Pelican feed links
- Add recommended HEAD elements (https://github.com/joshbuchea/HEAD)
- Use minified css assets
- Link to boostrap, clean-blog and font-awesome stylesheets
- Add theme options, better options names

Template consistency, update structure on base.html

Fix missing article summary on index.html

Show the article.summary for teasers

alchemy/templates/author.html

@@ -1,9 +1,9 @@
 {% extends "index.html" %}
 
 {% block title %}
-  {{ SITENAME }} — Articles by {{ author }}
+{{ author }} Articles — {{ SITENAME }}
 {% endblock %}
 
-{% block page_title %}
-  <h1>Articles by {{ author }}</h1>
+{% block page_header %}
+{{ author }} Articles
 {% endblock %}