Changing to new theme and new structure

[bedroesb]

Since the theme is being previewed from my fork I thought it would be easy to work on it immediately. Normally you should have access to it with this PR.

LIVE PREVIEW HERE

• [x] Restructuring the main landing page
• [x] Making a landing page for the documentation, or do we take Johan his page ? I now placed his content in "start guide"
• [x] Maybe we want "quick start guide" and "full guide" from Johan in de side menu
• [x] Prune the old pages, maybe get rid of them
• [x] Move events to new system
• [x] Adding the correct redirects
• [x] Making sure all urls work
• [x] Getting rid of the collapsible peices and other html snippets that are not needed anymore