Add IUserPasswordStore<T> support

- Store the password hash with the user data, so add column to schema
- For now, let's not expose the extra properties outside of what IUser<T> forces us to, so make the new property on CassandraUser internal
- We now need to support UpdateAsync, so add statements for those to update both user tables
Add back IUserSecurityStampStore<T> support

- Same as last commit, keep properties internal for now, store on user object, write them on create/update to both user tables