Add report_report_object table to data model

In order to associate report objects with reports, we need another table in the data model. The table should look something like this (feel free to edit/change/improve):

#----------------------------

1. Table structure for report_report_object
   #----------------------------
   CREATE TABLE report_report_object (
   report_id int(11) NOT NULL default '0',
   report_object_id int(11) NOT NULL default '0',
   PRIMARY KEY (report_id,report_object_id),
   KEY report_report_object (report_id),
   CONSTRAINT report_report_object_report_ref FOREIGN KEY (report_id) REFERENCES report (report_id),
   CONSTRAINT report_report_object_report_object_ref FOREIGN KEY (report_object_id) REFERENCES report_object (report_object_id)
   ) ENGINE=InnoDB DEFAULT CHARSET=utf8;