don't pass "~ " to new Metis

tuning

gracefully handle the case where a constant is partially or not instantiated at all, as may happen when reconstructing Metis proofs for polymorphic type encodings

temporarily document "metisX"

use "metisX" as fallback, since it's much faster than "metisFT"

temporarily added "MetisX" as reconstructor and minimizer

ensured that the logic for "explicit_apply = smart" also works on CNF (i.e. new Metis)

show what failed to play

refined auto minimization code: don't use Metis if Isar proofs are desired, and fall back on prover if Metis is too slow

tuning