List of changes:
* configurable unenrol action
* cron period increased to 1 hour in order to lower server load, courses should not get out of sync often
* CLI sync script for debugging or manual sync after configuration change
* phpdocs fixes
* when plugin is disabled all roles are removed, enrollments are kept
* uninstall script
* other bugfixing and performance improvements
* handlers can be defined as internal or external
* external handlers are not called instantly when inside DB transaction
* code cleanup
* more robust detection of broken handlers
* refixed unit tests
* removing all pending events from 1.9 - these can not be processed due to encoding changes
* finally using real 'component' in handlers table