Allow to lower the feedback level per application

We munge the application id the same way as it's done
for notifications so these can eventually move into
the same schema.

data/org.sigxcpu.feedbackd.gschema.xml

@@ -17,14 +17,6 @@
   </schema>
 
   <schema id="org.sigxcpu.feedbackd.application">
-    <key name="application-id" type="s">
-      <default>''</default>
-      <summary>Application ID</summary>
-      <description>
-        The application that this policy is for.
-      </description>
-    </key>
-
     <key name="profile" type="s">
       <choices>
         <choice value='full'/>