Add commented-out unicode normalization option

* ../import/import.properties: Add commented-out unicode normalization
  option.

import/import.properties

@@ -31,3 +31,17 @@ marc.to_utf_8 = true
 marc.permissive = true
 marc.default_encoding = BESTGUESS
 marc.include_errors = true
+
+# Perform Unicode normalization.
+#
+# Allowed values are:
+#
+#   C  - Normalization Form C (NFC)
+#   D  - Normalization Form D (NFD)
+#   KC - Normalization Form KC (NFKC)
+#   KD - Normalization Form KD (NFKD)
+#
+# For the differences of the normalization forms see the Unicode
+# Standards Annex #15, located at <http://unicode.org/reports/tr15/>.
+#
+# marc.unicode_normalize = C