[rbp] Default extract thumbnails to false

It can take 80 seconds for a single file on a Pi. It can cause crashes with out-of-memory errors.
It genereates a lot of support issues. Best to default to disabled and let users enable it if they must

system/settings/rbp.xml

@@ -43,6 +43,12 @@
         <setting id="myvideos.extractchapterthumbs">
           <default>false</default>
         </setting>
+        <setting id="myvideos.extractflags">
+          <default>false</default>
+        </setting>
+        <setting id="myvideos.extractthumb">
+          <default>false</default>
+        </setting>
       </group>
     </category>
   </section>