openolat#264: new role coursereader for read-only access to the list of courses, their configuration and the members

openolat#263: do add classes without o_icon prefix also to the surrounding div to be able to disable entries

And make delete task slightly more frightening

And add .zip to zip archives

Use a single algorithm to generate the authentication user name for OLAT
provider and write in the confirmation E-mail this username.

has no authentication at all