Changes

tsk28 Adds visits attribute to the Story entity
Adds to the Story entity the attribute visits to be able to count the
number of visits

tsk28 Modifies tests of the Story entity with the new visits attribute
Modifies existing tests and add new tests of the Story entity after
adding the new attribute visits

tsk28 Modifies test resources with new Story entity attribute
Modifies functions and data used by all tests to add the new visits
attribute of the Story entity

tsk28 Modifies the example data to add the attribute visits
Modifies the scripts with the sample data from additional-material to
add the new column visits in the insert statements