Make exp. expr output more readable/like PUBS
Strategy: More chaining, less exponential RFs
Strategy: Limit number of chaining steps.

Practice shows that we never do more than 15 steps. This should probably
be related to the size of the system, but I can't be bothered right now.
Strategy: Do not use RTA'11 for degree 1, subsumed by Farkas-based

(tested on the whole benchmark set)
Improve separation heuristic
Resort to standard analysis if separated analysis failed
Do not separate if we are modifying _all_ vars
Strategy: Less Polo2 proving