Detect and skip non-parent index-organized tables

As described in the Oracle frequent problems section, we can run into situations during the snapshot where we attempt to perform a lock or select against a table that is a child index-organized table that has no knowledge of its overflow counterpart, which leads to a ORA-25191 exception.

We should be able to detect these child index-organized tables and omit them from the snapshot by default as to avoid the ORA-25191 error and not enforce any special configuration changes on the part of the user.