ncm-sysconfig: Break apart schema for clarification

* Add annotations based on paraphrased description from pod.

ncm-sysconfig/src/main/pan/components/sysconfig/schema.pan

@@ -7,9 +7,20 @@ declaration template components/sysconfig/schema;
 
 include 'quattor/schema';
 
+@documentation{
+Contents of a sysconfig file modelled as a dict of key-value pairs.
+
+Two reserved keys C<< prologue >> and C<< epilogue >> are treated specially,
+their values will be copied verbatim into the file before or after the key-pair definitions.
+}
+type component_sysconfig_file = string(1..){};
+
 type component_sysconfig = {
     include structure_component
-    'files' ? string(1..){}{}
+    @{
+    dict of dicts with a file name as the first key and the contents of each file as the child dict.
+    }
+    'files' ? component_sysconfig_file{}
 };
 
 bind '/software/components/sysconfig' = component_sysconfig;