Remove minimized_constraints method from PPLProperty.

This is an internal PPL method and should not be exposed in the
Jandom interface.
Slight increase in precision for BoxDouble over reals.
Fix linearInequality for parallelotopes of dimension 0.
Remove useless return statements.
Improve precision of the sum domain in limit cases.
Fix isTop for the sum domain.
Remove test which is not guaranteed to be true in every domain.
Add comment to BoxDoubleDomainSuite over doubles.
Add a generic test on the effect of unsatisfiable linear forms.
Add more properties to test for Int+Parallelotopes.
Assortment of fixes.
Add constraints and isPolyedral methods to numerical domains.
Add tests for isPolyhedral and constraints methods.
Add a benchmark program for Int+Parallelotopes.