Refactored CnfStream to work with the bv theory Bitblaster:

Refactored CnfStream to work with the bv theory Bitblaster:
    * separated SatSolverInput interface class into two classes:
           - TheoryProxy for the sat solver to communicate with the theories
           - SatSolverInterface abstract class to communicate with the sat solver
    * instead of using #ifdef typedef for SatClauses and SatLiterals, now there are CVC4 SatLiteral/SatClause types and mappings between them and the internal sat solver clause/literal representation
    * added abstract classes for DPLLSatSolver and BVSatSolver different interfaces

Replaced TheoryBV with bitblasting implementation:
    * all operators bitblasted
    * only operator elimination rewrite rules so far