[IMP] event: improve report naming and use print_report_name

Purpose of this commit is to clean and uniformize report naming through
various addons. It has been chosen to name them using a formatting like
<report_name> - <object_name or suffix> .

addons/event/report/event_event_reports.xml

@@ -24,10 +24,9 @@
         report_type="qweb-pdf"
         name="event.event_registration_report_template_badge"
         file="event.event_registration_report_template_badge"
-        paperformat="event.paperformat_euro_lowmargin"/>
-    <record id="report_event_registration_badge" model="ir.actions.report">
-        <field name="print_report_name">'Registration Event'+'-'+(object.name)</field>
-    </record>
+        paperformat="event.paperformat_euro_lowmargin"
+        print_report_name="'Registration Event - %s' % (object.name).replace('/','')"
+    />
 
      <report
         id="report_event_event_badge"