Refactor docs-ng to Python and add comprehensive self-documentation - #26

Changed pages include:

• index.html - view
• 404.html - view
• contributing/index.html - view
• explanation/index.html - view
• how-to/index.html - view
• overview/index.html - view
• reference/index.html - view
• tutorials/index.html - view
• contributing/security.html - view
• contributing/testing/index.html - view

There are more changes not included in the list