Added "RSS email: with user name" format for email fields, fixed empty <guid> element showing even if not defined

Initial version of 7.x-2.x branch, during a major rewrite. Definitely not finished yet, most of the main features should already work fine though.

Issue #1400942 by miiimooo: Replaced drupal_add_link() with drupal_add_html_head_link() and abslute URL for feed icon

switched is_numeric for isset in non-empty check to avoid empty strings, which can be passed by views numeric handlers

#585720 disappearing feed icon, added views attach_to method. #779760 undo double checkplain on node title and similar field handlers

  handling.