"The breadth of the general definition makes it vital to come within the terms of a carve-out if one is available. However, the carve-outs are not available to a person who admits to being an ERISA fiduciary.... [E]ven for advisers and financial institutions that undertake the many compliance duties and disclosures necessary to come within the 'best interest contract' exemption, in the end, the exemption only exempts the person from the prohibited transaction rules, including potential excise taxes for IRAs under the Internal Revenue Code.... [T]he exemption does not exempt a person... from the general fiduciary duties under ERISA ... or from potential civil liability to make up any loss to the plan resulting from a breach of those duties."