Codechecker review

Hello,

I am developing a new activity module (https://github.com/danielneis/moodle-mod_webrtcexperiments/)
and used the Moosh tool (https://github.com/tmuras/moosh) to create the basic structure based on this template and ran https://github.com/moodlehq/moodle-local_codechecker against it.
There is a lot of fixes, hope that you like =)

Kind regards,
Daniel