Improve handling of use_remote_estimate, local_tuple_estimate, and row_estimate_method options

[GeoffMontee]

There are various problems with the use_remote_estimate, local_tuple_estimate, and row_estimate_method options, including (but probably not limited to):

1. I think use_remote_estimate only expects 0 or 1. Obviously, it would also make sense to look for true or false.
2. If you set use_remote_estimate to some value other than 0, then I think local_tuple_estimate will be ignored.

See #385 for some implications of this.