Make it easier to deploy HTML5-version

[adewes]

Currently, the normal version of Github uses hashtag-based navigation.

We have also implemented HTML5-based navigation, which requires running a server that will redirect all nested URLs to the app page though (i.e. "/milestones/adewes/gitboard" should be a valid URL and render the same page as "/").

Currently, enabling HTML5-based navigation requires the following steps:

• Replace all relative URLs in templates/index.html and the config.js with absolute paths.
• Use settings_html5_navigation.js as the main settings file

We could solve this in a more intuitive way by having Make generate settings and template files with the appropriate content, e.g. using Jinja to process templates.