Settings: add an oem-setup entry

- Add independent oem-setup entry to the example configuration.
 - Document that things may have a default value (so you don't **have**
   to set them in the file) but that Calamares will complain.

settings.conf

@@ -128,7 +128,8 @@ branding: default
 
 # If this is set to true, Calamares will show an "Are you sure?" prompt right
 # before each execution phase, i.e. at points of no return. If this is set to
-# false, no prompt is shown. Default is false.
+# false, no prompt is shown. Default is false, but Calamares will complain if
+# this is not explicitly set.
 #
 # YAML: boolean.
 prompt-install: false
@@ -142,16 +143,23 @@ prompt-install: false
 # setting. (e.g. partitioning seems like a bad idea, since that is expected to
 # have been done already)
 #
-# Default is false (for a normal installer).
+# Default is false (for a normal installer), but Calamares will complain if
+# this is not explicitly set.
 #
 # YAML: boolean.
 dont-chroot: false
 
+# If this is set to true, Calamares refers to itself as a "setup program"
+# rather than an "installer". Defaults to the value of dont-chroot, but
+# Calamares will complain if this is not explicitly set.
+# oem-setup: true
+
 # If this is set to true, the "Cancel" button will be disabled.
-# This can be useful if when e.g. calamares is used as a post-install configuration
+# This can be useful if when e.g. Calamares is used as a post-install 
-# tool and you require the user to go through all the configuration steps.
+# configuration tool and you require the user to go through all the 
+# configuration steps.
 #
-# Default is false.
+# Default is false, but Calamares will complain if this is not explicitly set.
 #
 # YAML: boolean.
 disable-cancel: false