Attempt at an iInduction tactic.
This comment mostly addresses issue #34. There are still some issues: - For iLöb we can write `iLöb (x1 .. xn) as "IH"` to revert x1 .. xn before performing Löb induction. An analogue notation for iInduction results in parsing conflicts. - The names of the induction hypotheses in the Coq intro pattern are ignored. Instead, when using `iInduction x as pat "IH"` the induction hypotheses are given fresh names starting with "IH". The problem here is that the names in the introduction pattern are idents, whereas the induction hypotheses are inserted into the proof mode context, and thus need to have strings as names.