makes a scatterplot of corrections coming either from reports (if xml geometries are None) or from geometryX and geometryY (WRT the common initial geometry0)
"param" may be one of "deltax" (Delta x position residuals), "deltadxdz" (Delta (dx/dz) angular residuals), "curverr" (Delta x * d(Delta q/pT)/d(Delta x) = Delta q/pT in the absence of misalignment)