Course Specific Role for non-existing users

It should be possible to invite someone to a course specific role without that person being a user in the system yet. When doing so, a name of this person should also be supplied as placeholder until they make an account. When they make an account, the role should be linked to the proper user.

Similar behavior exists already for the role invitations for companies. It may be possible to copy some of that logic / abstract this logic into a concern.

• Add LDAP integration (see !630 (closed))
• Create a method to create users by their TU Delft email address based on LDAP info
• When an email address of a non-existent user is entered and that email address ends in "@tudelft.nl" or "@student.tudelft.nl"
• Add "from-ldap" status to created_via in user
• Assign "from-ldap" status to the newly-created user
• Handle users with a different LDAP email than the one in projectforum

.

• Add a name field to course specific roles on project proposal (do not use when user exists)
• Add name and email fields to user course specific role
• Make .user return a fake user with that name and email with no id (or -1, check) - change belongs_to :user, make optional and create a .user method
• Make the name of the user be appended by " (Unregistered)" when accessing a fake user via .user
• When a user registers, actually link user course specific roles to that new user based on the email

Related to #249 (closed)