The representation of formulas in a proof goal that are more complex than
simple facts. Such formulas are considered to have positive
polarity, i.e., as conjunctions in the succedent of a goal.
This class is both responsible for storing such formulas and for eventually
processing the formulas, e.g. by splitting up the formulas/proof goal.
Return true if f is a formula that can be handled
by this task
Create a new FormulaTask by updating the value of
Update the task with possibly new information from the goal