Add method to get probabilities of a single measurement on specific qubit

[SamarthH]

What is the expected behavior?

Single measurements do not output partial_probability in the result. Currently there is no direct way to get probabilities of a single measurement on specific qubit. Need to add a method to do the same. This is in reference to #11 point 2.

[SamarthH]

@sen-p , @shivalee12 , @NickelKiln : Is someone willing to take this up?

[shivalee12]

yes, I can try.