Renamed BosonOperator and FermionOperator

Renamed BosonOperator and FermionOperator BosonOp and FermionOp, to be consistent with how other model specific operators are named in sympy.physics.quantum (e.g. the operators in the spin module).
Updated docstring tests to new module imports
restored (anti)commutation relations for independent bosonic (which was lost in the restructuring of the modules)