FlatDetector: long c'tor instead of setter fcts

auto/Examples/scatter2d/AxesInDifferentUnits.py

@@ -17,11 +17,8 @@ def get_sample():
 def get_simulation(sample):
     beam = ba.Beam(1e9, 1*angstrom, 0.2*deg)
     n = 500
-    detector_distance = 2000.0  # in mm
     width = 170  # nm
-    height = width
-    detector = ba.FlatDetector(n, width, n, height)
-    detector.setPerpendicularToSampleX(detector_distance, width/2., 0)
+    detector = ba.FlatDetector(n, n, width, width, beam, ba.FlatDetector.X, 2000.)
 
     simulation = ba.ScatteringSimulation(beam, sample, detector)
     return simulation