The documentation of, and the 'ssh ... --help' page for LsUserRefs
showed the project and user options as optional although they were
required. We now mark them as required in their annotations. Thereby,
the 'ssh ... --help' page lists them as required, and it is
automatically assured that they are not null. We also marked them as
required in the documentation.
Change-Id: I73aace6eeebb897174628c444350a275b323b673
a0e111ea75