Add concordance lists (moved from MDImporter)

README.md

@@ -1,3 +1,5 @@
-# importer-concordance-lists
+# Concardance Lists for Imports to museum-digital
 
-Concordance lists for automatically categorizing and correcting controlled entry types during imports to museum-digital.
+This directory contains concordance lists for accepted values. Where e.g. an entry type may be identified at museum-digital only by its ID, it is not realistic to expect providers of import data (which is to say: museums) to enter the entry type ID from museum-digital's relevant list. Hence, the lists contained in this subdirectory provide human-readable names for the IDs accepted by museum-digital as found in previous imports, so that they can be automatically translated to the IDs and names as used within the context of museum-digital.
+
+The lists are grouped as class constants of their relevant entry type. All class names may be prefixed with _MDConc_.