update docs, change_table does not use TableDefinition.
Support PostgreSQL specific column types when using `change_table`.

Closes #9480.

We use `TableDefinition` for `#create_table` and `Table` for `#change_table`.
The PostgreSQL sepcifc types were only defined on `TableDefinition` so I
also added them to `Table`.
Merge pull request #9484 from senny/9480_change_table_and_hstore

Support PostgreSQL specific column types when using `change_table`.

We use `TableDefinition` for `#create_table` and `Table` for `#change_table`.
The PostgreSQL sepcific types were only defined on `TableDefinition` so they needed to be added to `Table` as well.