Manually attach the column to the table in `View` construction
Manually attach the column to the table in `View` construction

For some reason, in the sqlalchemy
commit:aceefb508ccd0911f52ff0e50324b3fefeaa3f16
in lib/sqlalchemy/sql/elements.py, the `ColumnClause._make_proxy`
method does not automatically attach the column anymore.

This is now done manually.

Refs #471

agdsn/pycroft,agdsn/pycroft,agdsn/pycroft,agdsn/pycroft,agdsn/pycroft