Doxygen theme to style HTML output similar to Github Markdown

This is a minor tweak of the template provided from piconomix.

• The position of search engine can be changed by running search_egeine_change.py.
• Header titles can be added on member pages by running header_change.py.
• The position of the link to Doxygen page was modified in doxygen_header.html.

An example of this tweak version can be found here.