The NodeEvaluation makes it difficult to use a course node in the
learning path access concept. So it is refactored to a minimum extent,
so that it can covering the previous functionality.
As a replacement a new security callback and a new tree node type is
introduced.

OO-1812: only load the users which are shown in a list, make the e-mail visible for all users if configured

OO-1683: extended Nodeconfiguration, added config-pane in editcontroller, implemented config validation & migration

OO-1068: reduce the rights of guest in calendar  and members course elements, fix some small issues in CSS of calendar for guest, fix missing translation in DEN