removes almost all PHP warnings and notices for the student user type
removes almost all PHP warnings and notices for the switcher user type
videochat fixes for the student user type
removes almost all PHP warnings and notices for the tutor user type
added png image type support
switcher address book now loads all students registered in the provider
removes almost all PHP warnings and notices for the author user type
fixed calendar image path in template
bug fix in fillAddressBook method
some more warnings removal
removes almost all PHP warnings and notices for the admin user type
Merge branch 'warning-suppression'
Merge branch 'master' into ada-api