Allow only coordinators to import projects from and to course editions
Currently, only coordinators have access to importing projects from and to course editions. This also affects copying a single project from the project page.
In order for someone to be able to import projects, they must be a coordinator in both editions. Perhaps this might cause issues if a course changes coordinators and the new coordinator wants to import projects from the old edition?
This is done via abilities, so administrators can do anything they want.
Closes #505
Edited by Martin Mladenov