Remove m_cell_global_index from Connectivity

• now this information is computed when needed (load balance)
• closes #11 (closed)

src/utils/PartitionerOptions.hpp

@@ -43,9 +43,7 @@ getPartitionerEnumFromName(const std::string& enum_name)
       return PartitionerEnumType{enum_value};
     }
   }
-  // LCOV_EXCL_START
-  throw UnexpectedError(std::string{"could not find '"} + enum_name + "' associate type!");
-  // LCOV_EXCL_STOP
+  throw NormalError(std::string{"could not find '"} + enum_name + "' associate type!");
 }
 
 class PartitionerOptions