Manage calculation of translations from a formula

In some case the .h5 file can contains information on several motor but not directly the translation. To obtain it we should be able to use a formula with integer / float value + existing motor keys like for ID11:

 x_translation = diffty - d1ty ( - 14)   #(centre of rotation compared to detector)
 y_translation = difftz + samtz - d1tz  # (sample height)
 z_translation = nfdtx - 150               #(offset)