CC-3636: Media Folder: dir path in cc_music_dir should be in consistent format

- DateHelper.php is moved from model to common folder
- created OsPath.php file which contains normpath()
- normpath() is used instead of realpath()

airtime_mvc/application/common/OsPath.php

@@ -0,0 +1,45 @@
+<?php
+class Application_Common_OsPath{
+    // this function is from http://stackoverflow.com/questions/2670299/is-there-a-php-equivalent-function-to-the-python-os-path-normpath
+    public static function normpath($path)
+    {
+        if (empty($path))
+            return '.';
+    
+        if (strpos($path, '/') === 0)
+            $initial_slashes = true;
+        else
+            $initial_slashes = false;
+        if (
+            ($initial_slashes) &&
+            (strpos($path, '//') === 0) &&
+            (strpos($path, '///') === false)
+        )
+            $initial_slashes = 2;
+        $initial_slashes = (int) $initial_slashes;
+    
+        $comps = explode('/', $path);
+        $new_comps = array();
+        foreach ($comps as $comp)
+        {
+            if (in_array($comp, array('', '.')))
+                continue;
+            if (
+                ($comp != '..') ||
+                (!$initial_slashes && !$new_comps) ||
+                ($new_comps && (end($new_comps) == '..'))
+            )
+                array_push($new_comps, $comp);
+            elseif ($new_comps)
+                array_pop($new_comps);
+        }
+        $comps = $new_comps;
+        $path = implode('/', $comps);
+        if ($initial_slashes)
+            $path = str_repeat('/', $initial_slashes) . $path;
+        if ($path)
+            return $path;
+        else
+            return '.';
+    }
+}