Checking for integer instead of int for summable columns.
Add spec for WorkPackagesController#column_data

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Spec WorkPackagesController integer column summing

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Fixed spec.
Throwing exception if unknown column name is passed to column_data.
Fix integer attr. used in WorkPackagesController spec

`story_points` is only available with openproject-backlogs installed.

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Merge pull request #1107 from opf/bug-5770-summing-integer-columns

Checking for integer instead of int for summable columns.