Merge branch 'install_28_STABLE' of https://git.in.moodle.com/amosbot/moodle-install into MOODLE_28_STABLE

In short, when a user is creating a new course they can set
the ID number, shortname, fullname and summary. However, when
they merge a backup into a course they need the permissions to do so.

Changed in May 2016.

Merge branch 'install_28_STABLE' of https://git.in.moodle.com/amosbot/moodle-install into MOODLE_28_STABLE

Merge branch 'install_28_STABLE' of https://git.in.moodle.com/amosbot/moodle-install into MOODLE_28_STABLE

Merge branch 'install_28_STABLE' of https://git.in.moodle.com/amosbot/moodle-install into MOODLE_28_STABLE

    Also unit tests were added to cover the new clean_data() method.

    Also the get_property_definition() was created to get the property without retrieve the whole definition cache and
    unit tests were created to tests those new methods.

Thank you to Zachary Durber for originally working on this issue.

When getting the navigation branch data through AJAX, require
login if forcelogin is set.

Singleview users must have Manage Grade permission to modify the
Exclude grade attribute.