Add `angularFrame `and `qSpaceFrame` to Frame Python API

Implements Frame transformations between q and angular coordinates.

Datafield::crop is repaired.

Couple of assertions was removed from projections; they often fail due to rounding error.

Base/Axis/Frame.cpp

@@ -138,6 +138,26 @@ Frame* Frame::plottableFrame() const
     return new Frame(std::move(outaxes));
 }
 
+Frame* Frame::angularFrame(double lambda, double alpha_i) const
+{
+    ASSERT(rank() == 2);
+
+    auto* phi_f_scale = new Scale(xAxis().phi_f_Scale(lambda));
+    auto* alpha_f_scale = new Scale(yAxis().alpha_f_Scale(lambda, alpha_i));
+
+    return new Frame(phi_f_scale, alpha_f_scale);
+}
+
+Frame* Frame::qSpaceFrame(double lambda, double alpha_i) const
+{
+    ASSERT(rank() == 2);
+
+    auto* qy_scale = new Scale(xAxis().qy_Scale(lambda));
+    auto* qz_scale = new Scale(yAxis().qz_Scale(lambda, alpha_i));
+
+    return new Frame(qy_scale, qz_scale);
+}
+
 Frame* Frame::flat() const
 {
     std::vector<const Scale*> outaxes;