instead of using three Vectors (formulaVariableNames, formulaVariableColumns...
- remove template so there is no need to include ColumnPrivate header into Column. This is done, because Column.h gets included already in the ColumnPrivate.h so there would by a cycle
- instead of using three Vectors (formulaVariableNames, formulaVariableColumns and formulaVariableColumnPaths) Which have to be synched, use a struct and store the data in there. So it is much easier to sync
fixes #30 (closed)