Made it possible to bypass file extension check.
Merge branch 'master' into user-results

Conflicts:
	h5p-php-library
Merge branch 'user-results' into whitelist
Merge branch 'user-results' into whitelist
Lastest lib.
Merge branch 'user-results' into whitelist

Conflicts:
	h5p-php-library
Prevent double slashes in file paths.
Merge branch 'master' into whitelist
Improve compability with other plugins. Footer doesn't have to be printed before scripts anymore.
Merge branch 'master' of github.com:h5p/h5p-wordpress-plugin

Conflicts:
	public/scripts/h5p-integration.js
Use latest editor css.
Merge branch 'master' into user-results

Conflicts:
	h5p-php-library