Use Composer to pull in required modules

Problem/Motivation

Currently opigno_ilt requires the following:

- group:group
- opigno_calendar:opigno_calendar
- opigno_calendar_event:opigno_calendar_event
- opigno_cron:opigno_cron

However on install, these modules may not be present in the codebase.

Proposed resolution

Add modules to composer.json require.