Detector2D now parameterized through width and center in phi,alpha (#854)

Some code duplication in the GUI (Axis -> Span property and form), to be revised later.

Resolves #854 (closed).

GUI/Model/Descriptor/SpanProperty.cpp

@@ -22,8 +22,8 @@ namespace Tag {
 const QString Nbins("Nbins");
 const QString Width("Width");
 const QString Center("Center");
-const QString Min("Min"); // from AxisProperty pre v22
-const QString Max("Max"); // from AxisProperty pre v22
+const QString Min("Min");                       // from AxisProperty pre v22
+const QString Max("Max");                       // from AxisProperty pre v22
 const QString ExpandGroupbox("ExpandGroupbox"); // from AxisProperty pre v22
 
 } // namespace Tag