Externally controlled sort improvements

[adam-thomas-privitar]

Currently, the sort hook provides a way to have sort from an external source, like an API by activating the manualSortBy option. However, I think this doesn't go far enough since if the state of the sort is externally provided, it means ideally:

1. That state should not be copied into react tables state (duplication of state, leads to things getting out of sync).
2. You want to respond to reqeusted changes in the sort (i.e. click on table header) via some callback passed into react-table. For example onSortChanged.

This way the sort state can be fully controlled which makes more sense than uncontrolled in these cases.

For columns in controlled mode, the hooks function would be a lot simpler, and would just map through the sort state passed through the useTable hook args and. also the click handler. This would be decided on a per column level, maybe using a column option like sortControlled or something. Arguably you could mix both controlled (api powered) and uncontrolled (client side) sorts simultaneously.