Fix wrong comments for attribute exploration

Signed-off-by: Daniel Borchmann <daniel.borchmann@mailbox.tu-dresden.de>
Add missing feature for exploration with incomplete counterexamples

Removing crosses from the possible context now which
are not possible anymore, as adding them would result
in a contradiction to what is known from the certain
context

Signed-off-by: Daniel Borchmann <daniel.borchmann@mailbox.tu-dresden.de>
Adding simple test case for exploration with incomplete counterexamples

Signed-off-by: Daniel Borchmann <daniel.borchmann@mailbox.tu-dresden.de>