MDL-31625 fix multiple global search-replace issues

Includes following fixes:
* support for MS SQL Server
* optional trimming of of oversized VARCHAR fields
* conversion to forms library
* full localisation
* other cleanup

lib/adminlib.php

@@ -6741,11 +6741,8 @@ function db_replace($search, $replace) {
 
         if ($columns = $DB->get_columns($table)) {
             $DB->set_debug(true);
-            foreach ($columns as $column => $data) {
-                if (in_array($data->meta_type, array('C', 'X'))) {  // Text stuff only
-                    //TODO: this should be definitively moved to DML driver to do the actual replace, this is not going to work for MSSQL and Oracle...
-                    $DB->execute("UPDATE {".$table."} SET $column = REPLACE($column, ?, ?)", array($search, $replace));
-                }
+            foreach ($columns as $column) {
+                $DB->replace_all_text($table, $column, $search, $replace);
             }
             $DB->set_debug(false);
         }
@@ -6776,6 +6773,8 @@ function db_replace($search, $replace) {
         echo $OUTPUT->notification("...finished", 'notifysuccess');
     }
 
+    purge_all_caches();
+
     return true;
 }