Ordered BAPA solver is now re-entrant :P (still not thread-safe)

src/orderedsets/AST.scala

src/orderedsets/Main.scala

src/orderedsets/MyZ3Context.scala

src/orderedsets/Phase2.scala

src/orderedsets/Phase3.scala

src/orderedsets/QFBAPAtoPATranslator.scala

src/orderedsets/Symbol.scala

testcases/SetOperations.scala