Support alpha and lambda distributions in Offspec and Depthprobe

From DepthprobeSimulation::runComputation(..) and OffspecSimulation::runComputation it can be seen that existence of alpha/lambda distributions is ignored and only m_scan->wavelength() and bin centers of the axis are used. Moreover, wavelength is equal to zero if the lambda distribution is set, which leads to exceptions in other parts of computational core.

• Depthprobe
• Offspec