Add decompositions for rotation + cx set

[TheGupta2012]

Related to #103

• Define decompositions to rotation + cx set.
• Conversions will have 2 parameters - decomposition algorithm AND source basis set

class RotationCXDecomposer: 
        def __init__(self, algorithm, source_basis):
           pass 
        def convert(qasm_module): 
           # converts the gates to rotation + cx set in place 
           pass 

The map for the conversions can contain a callback function and the number of parameters.

[TheGupta2012]

Completed as part of #123