Added configurable template path via path_tpl env var (-T option to repo2html)

The .sh extension was removed from the commit filename to recognize the fact
that configurable templates may be any type of executable.
Added commit_html_* references to commit template, along with classes to support additional styling

This allows for simple configuration of the commit template. The intended use is
to either use a configuation script to export these values, or set a custom
template path and have the commit template set the values before exec'ing or
otherwise running the default script.

The template also now makes use of HTML5 tags, such as <article>.
Separated index HTML into its own template
Added .gitignore containing misc. build dotfiles
Commit template application now makes user of apply-template function
Added resume-default as abstraction for invoking default templates from custom overrides
Added external css configuration var and -C option
Additional configuration changes to default templates, including html_footer
Added custom template .config file support
Added html_index_footer, renamed {commit_html,html_commit}_footer
Added title and desc classes to index template