Added emergency exit sign template

- Added README files in Infrastructure and Physical

- Fix broken markdown links in index files

Contributions file changed to remove copyright assignment

- Moved content from root into structure of HOM

- Removed about.md, contributions.md and contact.md from root of repo

- Adding details to 'About this manual'

- Removing mention of UK from the top level
- Changed HoM to HOM trying for consistency
- Fixing broken links in the top level README.md

- Adding contribution documentation

First tagged release of the owners manual