Give a new name to the c_conj in the inner-product function

[Schoyen]

In the inner-product function we have implicitly assumed (via the naming of the arguments) that we are to compute the inner product of the same state vector c. However, this function is used for the inner product between any two state vectors a and b. Also, the user should still send in which of the two state vectors are complex conjugated. This allows for bivariational state vectors somewhere in the future.