Move meta content outside the docs content, create pages into the homepage project

[renoirb]

Some content is not related to docs and is published within the wiki.

The migration is about keeping documentation pages, other documents such as project documentation and other related content should be migrated elsewhere.

• Change location of pages?
  • WPD:About to go to www.webplatform.org/about ?
  • WPD:Policy to www.webplatform.org/policy ?
  • Pillars
  • Privacy Policy
  • Management
  • Administration
  • Projects
  • Infrastructure
• WPD:... content. Which one should we keep.