Implement direct message receive and background services manager, take 1.

 1. Background Service Manager Framework
    --Documentation provided in the main library/ajax/execute_background_services.php script.
    --Report at Administration->Reports->Services->Background Services
 2. Direct Message Receive
    --Service built on top of the Background Service Manager Framework
    --Can be set/modified in Administration->Globals->Connectors (bottom section)
    --Log can be viewed at Administration->Reports->Services->Direct Message Log
    --Added support for importing of documents with no patient mapping. GUI for
      this is at Miscellaneous->New Documents.
    --Added support for sending pnotes with no patient mapping.
    --Added support for service bots to enable storage of documents,
      sending of messages and accurate logging by services.

 Miscellaneous mods: Changed the Administration->Services to Administration->Codes in left_nav menu.
                     (to avoid confusion with the Services reports)
Couple minor fixes to previous Direct Messages Receiving commit.
Merge in Direct Service message receive and background service manager
Merge branch 'master' of git://github.com/openemr/openemr
Migrate the openemr/api/includes/pdflibrary folder to the openemr/library folder.