Add mine_functions to master config template

pillar.example

     file_roots:
       base:
         - /srv/salt
+    mine_functions:
+      network.interfaces: []
+      network.ip_addrs: []
+      grains.items: []
+
   minion:
     master: salt
     fileserver_backend:

salt/files/master.d/_defaults.conf

 #   web.*:
 #     - network.*
 #     - disk.*
+{% if 'mine_functions' in cfg_master %}
+mine_functions:
+  {% for name, roots in cfg_master['mine_functions'].items() %}
+  {{ name }}:
+    {% for mod in roots %}
+      - {{ mod }}
+    {% endfor %}
+  {% endfor %}
+{% elif 'mine_functions' in cfg_salt %}
+mine_functions:
+  {% for name, roots in cfg_salt['mine_functions'].items() %}
+  {{ name }}:
+    {% for mod in roots %}
+      - {{ mod }}
+    {% endfor %}
+  {% endfor %}
+{% endif %}
 
 
 #####         Logging settings       #####