Added tests for various installations types

- With root installation
 - Core css
 - App inside server root
 - Secondary apps directory outside server root
- With an installation in a sub directory
 - Core css
 - App inside server root
 - Secondary apps directory outside server root

Signed-off-by: John Molakvoæ (skjnldsv) <skjnldsv@protonmail.com>