Use lastest core fixes.
Implemented missing interface functions.

Conflicts:
	h5p-php-library
Use correct interface functions.
Merge branch 'master' of github.com:h5p/h5p-wordpress-plugin
Merge branch 'master' into user-results

Conflicts:
	h5p-php-library
Merge branch 'user-results' into whitelist
Merge branch 'master' into user-results

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