Remove m_cell_global_index from Connectivity

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

src/utils/PartitionerOptions.hpp

@@ -29,7 +29,7 @@ name(const PartitionerLibrary library)
   case PartitionerLibrary::PT__end: {
   }
   }
-  throw UnexpectedError("Linear system library name is not defined!");
+  throw UnexpectedError("Partitioner library name is not defined!");
 }
 
 template <typename PartitionerEnumType>