This commit merges in branches/arithmetic/internalbb up to revision 2831. This is...

This commit merges in branches/arithmetic/internalbb up to revision 2831.  This is a significant refactoring of code.

- r2820
-- Refactors Simplex so that it does significantly fewer functions.
--  Adds the LinearEqualityModule for handling update and pivotAndUpdate and other utility functions that require access to both the tableau and partial model.
-- Some of the code for propagation has moved to TheoryArith.
-r2826
-- Small changes to documentation and removes the no longer implemented deduceLowerBound() and deduceUpperBound().
- r2827
-- Adds isZero() to Rational. Adds cmp to DeltaRational.
- r2831
-- Refactored comparison to upper and lower in the partial model to use DeltaRational::cmp.
-- Refactored AssertUpper and AssertLower in TheoryArith to include functionality that has weaseled into TheoryArith::assertionCases.