Add doc for Multi-DB

Makefile

@@ -36,6 +36,10 @@ clean:
 
 update-qfq-doc:
 	rsync -av --delete --exclude=_make --exclude=_static extension/Documentation/ ../qfq-doc/Documentation/
+	cd ../qfq-doc
+	git commit -a
+	git push
+	cd ../qfq
 
 git-revision: make-dist-dir
 	echo $(GIT_REVISION_LONG) > $(DISTDIR)/revision.git

extension/qfq/qfq/Constants.php

@@ -795,6 +795,7 @@ const F_PARAMETER = 'parameter';    // valid for F_ and FE_
 
 // Form columns: via parameter field
 const F_DB_INDEX = 'dbIndex';
+const F_DB_INDEX_EXTRA = 'dbIndexExtra';
 const DB_INDEX_DEFAULT = "1";
 const PARAM_DB_INDEX_DATA = '__dbIndexData'; // Submitted via SIP to make record locking DB aware.