Adding error parametrization for MM simple clustering

This MR adds the options to use a parametrization (provided by @rosati) of the error in the MMSimpleClusterBuilderTool. In the default configuration the old error is used.

MuonSpectrometer/MuonReconstruction/MuonDataPrep/MMClusterization/src/SimpleMMClusterBuilderTool.cxx

@@ -192,13 +192,13 @@ StatusCode Muon::SimpleMMClusterBuilderTool::getClusters(std::vector<Muon::MMPre
     ///
     Amg::MatrixX* covN = new Amg::MatrixX(1,1);
     covN->setIdentity();
-    if(!m_useErrorParametrization){
+    if(!m_useErrorParametrization) {
       (*covN)(0,0) = 6.*(nmerge + 1.)*covX;
-    }else{
+      if(nmerge<=1) (*covN)(0,0) = covX;
+    } else {
       double localUncertainty = 0.074+0.66*theta-0.15*theta*theta;
       (*covN)(0,0) = localUncertainty * localUncertainty;
     }
-    if(nmerge<=1) (*covN)(0,0) = covX;
     ATH_MSG_VERBOSE(" make merged prepData at strip " << m_mmIdHelper->channel(MMprds[j].identify()) << " nmerge " << nmerge << " sqrt covX " << sqrt((*covN)(0,0)));
     
     ///