User defined flexicharge settings aren't inserted into the database

When one tries to add a flexicharge using one of the providers (e.g. Standard shipping, or a user defined provider), the additional charge settings defined in the provider module are not saved to the database. They are saved if you edit the newly created flexicharge and save the settings.

This problem occurs because of a malformed SQL query in flexicharge_admin_form_submit which leaves out the hide_if_zero value from the SQL INSERT query. I have attached a patch which fixes this bug.