Reshape jacobian of real input and complex output to ensure complex output

[mduschenes]

Reshape jacobian of real input and complex output to ensure complex output

• Currently jacobian() _make_vjp(fun,x) for real inputs and complex outputs yields grads with shape (ans.size*2,x.size), which is unable to be reshaped into jacobian_shape = (*ans.shape,*x.shape)
• jacobian() to include checks for real inputs and complex outputs (other combinations of input/output dtypes to be included)
• reshapes and transposes are done on grads to extract real and imaginary components of complex fun grads
• grads are recombined into complex number: grads.real - 1j*grads.imag (where the -1j convention is believed to be due to the form of the vjp)
• Tested personally on fun(x) with arbitrary x and fun shape
• CI unit tests to be conducted by admins, to include holomorphic/non-holomorphic checks etc. Thank you