CondEqual should give an error when constructed with vector length > 1

[mb706]

CondEqual$new(c("b", "c")))

should throw an error

[berndbischl]

not necessarily, unfortunately. it basically depends on whether we allow the parent param to be ParamUty (hence to use deps in learners).

if we allow that, such a param could have a vector-valued setting. i guess we don't want that, but this then need to make clear asserted

[mb706]

In that case the CondEqual test function is broken (should be identical instead of ==)