Tensor multiplication and factorization

Implement tensor multiplication and factorization to operate separately on qubit superpositions.

Currently an array of 3 qubits (thus a vector of 2^3 = 8 possible states) can only be used to apply three-qubit-gates (CCNOT or CSWAP), because the matrix representing the gate has to have the same side length as the superposition vector. To allow 1-qubit-gates (like the Pauli-X gate) to operate on multiple qubits, the tensor product is necessary to appropriately modify the gate matrix.

Still, the size of the superposition vector will grow exponentially to the amount of qubits. As long as these qubits are not entangled, they could be treated (and measured) separately. To implement this, tensor factorization is required.