[DEM-806] Binary controlled gates

[QFer]

• Parameter 'conditional' on the backend made True
• Generating the cqasm now via public method parse instead of calling the private methods from the circuit_parser
• Circuit parser parse method - checks if the instruction is a conditional or a 'normal'.
• In qiskit a conditional gate operation is based on an integer value of the classical registers, in cQASM the conditional gate is check against the positive value of bits. c_if(c, 11) actually means bit 2 and 4 must be false and bits 0,1 and 3 must be true. Because cQASM only checks for positive values of bits, bit 2 and 4 must be inverted before and after the gate operation.
• For each supported gate, a conditional gate cQASM generator is added.
• Unittests added for the new methods. All the possible exceptions are tested.
• Added the identity operator generating methods because it was in the basis_gates but not implemented.

[coveralls]

Coverage remained the same at 100.0% when pulling 020a957390dcc9068c726d945b5601d8943817f4 on feature/DEM-806/classical into 58cd50075f310aada11033d9513a1ca5cf2434b9 on dev.

[coveralls]

Coverage remained the same at 100.0% when pulling 4b1902e4f0995d6226464f9c8b816811167e2612 on feature/DEM-806/classical into 99d220b457fffbf166b601f1a53ded628396e6a2 on dev.