Custom storage key

[eire1130]

This pull request allows to define a custom storage key.

This is useful if you have multiple tables defined in the same namespace based on the same url.

For example, let's say we have two tables that the user can dynamically view.

1. user selects some page
2. user closes tableview by some mechanism

user opens table #2

1. user notices they are on page 2 already and cries.

[Mottie]

Thanks for sharing! Yeah, we definitely don't want crying users.