This will let the Issue Tracking, Gantt, and Calendar modules be enabled
or disabled as needed.  A database migration will enable the Gantt and
Calendar for all existing projects that have Issue Tracking enabled.

Contributed by Adam Soltys

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@4013 e93f8b46-1217-0410-a6f0-8f06a7374b81