See spec at:

• http://docs.moodle.org/en/Development:New_enrolments_in_2.0
• http://docs.moodle.org/en/Development:Enrolment_usage_overview

New tables:

• enrol - enrolment instances in each course
• user_enrolments - user enrolments, users may have several different enrolments in one course

Changes in tables:

• course - all enrol related fields migrated to new enrol table
• role_asignments - all enrol related fileds migrated to user_enrolments, new 'component' and 'enrolid' fields which allows us to properly protect enrol and auth role assignments

Enrol plugins:

• new enrollib.php with enrol related stuff and base enrol_plugin class
• necessary accesslib changes and new apis