Update Device Initializer for Netbox 2.7

The device database model has changed in Netbox 2.7.
Therefore the initializer code, that was used before, broke.
As a user, you will need to update your devices.yml file as
follows:

- Make sure the rack face is spelled lowercase.

See the diff of this commit for further information how this is meant.

initializers/devices.yml

@@ -1,9 +1,24 @@
+## Possible Choices:
+##   face:
+##   - front
+##   - rear
+##   status:
+##   - offline
+##   - active
+##   - planned
+##   - staged
+##   - failed
+##   - inventory
+##   - decommissioning
+##
+## Examples:
+
 # - name: server01
 #   device_role: server
 #   device_type: Other
 #   site: AMS 1
 #   rack: rack-01
-#   face: Front
+#   face: front
 #   position: 1
 #   custom_fields:
 #     text_field: Description
@@ -12,7 +27,7 @@
 #   device_type: Other
 #   site: AMS 2
 #   rack: rack-02
-#   face: Front
+#   face: front
 #   position: 2
 #   custom_fields:
 #     text_field: Description
@@ -21,7 +36,7 @@
 #   device_type: Other
 #   site: SING 1
 #   rack: rack-03
-#   face: Front
+#   face: front
 #   position: 3
 #   custom_fields:
 #     text_field: Description