Changed "method" NSPopUpButton to NSComboBox to accomodate WebDav/CalDav/custom HTTP methods

The NSComboBox allows a user to choose an established HTTP 1.1 method (GET, POST, PUT, etc.) or specify a WebDav/CalDav/custom methods (REPORT, PROPFIND, PROPPATCH, etc.). 

http://tools.ietf.org/html/rfc4791
http://tools.ietf.org/html/rfc4918

The requestMethodsWithBody logic was inverted to form requestMethodsWithoutBody, assuming only "GET", "DELETE", "HEAD", "OPTIONS" will not send a body, whereas all others will (including WebDav/CalDav/custom).