Support Higher Dimensional Ciphertexts and Keys for TFHE when Lowering RLWE to Polynomial

[lawrencekhlim]

Currently, our lowering for RLWE to Polynomial does not handle TFHE. Other schemes, like BGV have ciphertexts composed of 2 polynomials and a secret key composed of 1 polynomial; however, TFHE supports higher dimensional ciphertexts and Keys. See this link for details on TFHE encryption and decryption. Also, see LWEToPolynomial.cpp for where to adjust code.

See also #882.