Remove unneeded preloading of preferences
Namespace OrderPopulator reference in OrdersController so people don't run into potential issue where it would attempt to lookup a top-level OrderPopulator class
Fixed hardcoded paths to fontawesome

Fixes #2424
Allow payment method to control auto_capture?

Some gateways (ex. samurai, eway, stripe) only support purchase, not
auth/capture. This allows those gateways to override auto_capture?, and
coexist with other payment methods not using auto_capture, and also
eliminates the required configuration for those payment methods.

Fixes #2304