Sql Patch to update the user_externalaccount table.

Summary: Sql Patch to rename the externalaccount table to user_externalaccount and to add dateCreated, dateModified fields to the updated table.

Test Plan: {F41442}

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin, AnhNhan

Differential Revision: https://secure.phabricator.com/D5770