User with limited permissions should not be able to rename a table

[simonw]

I just succeeded in renaming a table when I had alter-table permission - but I did not have drop-table permission on the old name or create-table permission on the new name.

Found while working on:

• Tests that demonstrate table-level permissions #59

[simonw]

I want to display the "Rename table" form only if the user has permission to use it - which means they need to have drop-table permission on the current table and they need create-table permission on the database itself.

[simonw]

This was released in 0.8a0.