Finished porting LIsts
Merge remote-tracking branch 'upstream/ssr' into ssr-work
Basics: Commented out the attempt at the non-accepting fixpoint definitions.
Induction: Solved exercise andb_true_elim2.
Induction: Solved exercise basic_induction.
Induction: Solved exercise double_plus.
Induction: Solved exercise case_elim.
Induction: Solved exercise mulnC.
Induction: Solved exercise evenb_n__oddb_Sn.
Induction: Solved more_exercises.
Induction: Solved excercise eqnn.
Induction: Solved binary_commute.