classroom 6.x-1.0-beta7

This new beta release brings some new features (like the concept of 'course manager') and a lot of bugfixes. Here is summary of changes:

• Added the concept of course manager.
• UI improvements and fixes in Classroom Sign-up module.
• Feature #658330 by cross: add validation hook so user will see good description of error.
• Bug #663094 by manolopm: Task percentage can overdue 100% in assignments.
• Feature #663092 by manolopm: Activate course menu by default.
• Fixed assignments list to show student's final grade.
• Fixed assignments updating when no topic is selected.
• Fixed the 'Answer' link when viewing a answered assignment.
• Fixes and refactoring related to breadcrumbs.
• Other minor bugfixes.

Feedback is welcome!

Enjoy it!