Fix tptp proving by working around a hets problem Hets doesn't find a theorem when we pass it as an argument. For TPTP, we know that there can only be a single node and a single theorem, so we don't need to pass the theorems array. The same applies for parsing the output of the prove command.

Use original scope on theorems associations.

Allow to have an ActiveRecord::Relation as axioms.

Pass divided, goal-local timeout to Hets.

Prepare timeout for Hets.

Comment on the sentence preparation.

Fix preparing of sentences generating nil values.

Add prover to ProveOptions.

Add ProveOptions class.