Easy Digital Downloads - Gateway Fees 1.5.5

Fix: Gateway fee not removed when switching from a gateway that has a fee to one that does not.
Fix: Negative fees not appearing on checkout.

Fix: Improved accuracy of percentage based gateway fees.
Fix: The total at the bottom of checkout didn't always include gateway fees.
Fix: Gateway fees could not be negative.
Fix: Reduced the amount of logging being done.
New: Moved settings to a subsection of the Gateway section.

Fix: Fixed issue with fee being reset to 0 when it shouldn't by adding missing edd_gf_gateway js variable.