data tree CHANGE to clarify purpose, rename data path types

Clarify how the paths generated by lyd_path() can be used.

Fixes #1317
diff --git a/src/validation.c b/src/validation.c
index d823ee1..0bc5ac4 100644
--- a/src/validation.c
+++ b/src/validation.c
@@ -854,8 +854,8 @@
         }
         if (v && (v == LY_ARRAY_COUNT(slist->uniques[u]))) {
             /* all unique leafs are the same in this set, create this nice error */
-            path1 = lyd_path(first, LYD_PATH_LOG, NULL, 0);
-            path2 = lyd_path(second, LYD_PATH_LOG, NULL, 0);
+            path1 = lyd_path(first, LYD_PATH_STD, NULL, 0);
+            path2 = lyd_path(second, LYD_PATH_STD, NULL, 0);
 
             /* use buffer to rebuild the unique string */
 #define UNIQ_BUF_SIZE 1024