Add a category field to the tutorials table

[SirJakesalot]

Add a categories table and incorporate a category for each tutorial.

[SirJakesalot]

Using a schema of id, name

• Not going to cascade on update/delete because then all tutorials for that category would be lost if there was an accidental delete.
• Adding a category_id column to tutorials, this means that a tutorial can only fall under ONE category. This is a foreign key.

[SirJakesalot]

Updated the createtable.sql/data.sql scripts to include the added table/column.

[SirJakesalot]

Need to incorporate another table, tutorial_categories. The schema will consist of two foreign keys referencing a tutorial object to a category object. This will enable a tutorial falling under mutiliple categories and lead to a nice query convention in the DataModel.