Make non-recursive convertAffineTerm.

The method computeTerm was renamed to convertAffineTerm and
made non-recursive.  We also simplify the code and do not
descend too much into the term.
Simplified walkIntern
Handle more proof rules

Handle Tautology excludedMiddle1 and 2
Handle @intern of booleans to bool = true
Handle @intern of cc equalities (side swapping)