docs(cookbook): update samples to not pass null model to Table constructor rows

In nearly all the cookbook examples, the table-common mixin is used which calls the table constructor the init hook as follows:

`let table = new Table(this.get('columns'), this.get('model'), { enableSync: this.get('enableSync') });`

But model is null during init, which previously resulted in an error (#340) and as of #522 will trigger an assertion.

Please update the cookbook so the examples are usable and reflect the recommended pattern.