Better documentation for db file renaming

h2/src/docsrc/html/features.html

@@ -953,7 +953,7 @@ The following files are created for persistent databases:
 Database name and location are not stored inside the database files.
 </p><p>
 While a database is closed, the files can be moved to another directory, and they can be renamed
-as well (as long as all files start with the same name).
+as well (as long as all files start with the same name and the respective extensions are unchanged).
 </p><p>
 As there is no platform specific data in the files, they can be moved to other operating systems
 without problems.