CC-2950: Tell users if they are running an out-of-date version or not

Initial implementation.
- added some code in phone_home_stat to retrieve latest version from stat server
  and store result in db

- created new view helper VersionNotify.php, which queries and calculates version
  difference, then returns the necessary information in html to the view files

- created new javascript file versiontooltip.js, which sets up the qtip stuff so that
  when the version notification icon is clicked, a tooltip is displayed

airtime_mvc/application/views/helpers/VersionNotify.php

@@ -0,0 +1,61 @@
+<?php
+
+/**
+ * This file does the following things:
+ * 1. Calculate how many major versions back the current installation
+ *    is from the latest release
+ * 2. Returns the matching icon based on result of 1, as HTML
+ * 3. Returns the matching tooltip message based on result of 1, as HTML
+ *    (stored in pair of invisible div tags)
+ * 4. Returns the current version, as HTML (stored in pair of invisible div tags)
+ */
+class Airtime_View_Helper_VersionNotify extends Zend_View_Helper_Abstract{
+    
+    public function versionNotify(){
+        if(Application_Model_Preference::GetPlanLevel() != 'disabled'){
+            return "";
+        }
+        
+        // retrieve and validate current and latest versions,
+        $current = Application_Model_Preference::GetAirtimeVersion();
+        $latest = Application_Model_Preference::GetLatestVersion();
+        $pattern = "/^([0-9]+)\.([0-9]+)\.[0-9]+/";
+        preg_match($pattern, $current, $curMatch);
+        preg_match($pattern, $latest, $latestMatch);
+        if(count($curMatch) == 0 || count($latestMatch) == 0) {
+            return "";
+        }
+        
+        // Calculate version diff
+        // Note: algorithm assumes the number after 1st dot never goes above 9
+        $diff = (intval($latestMatch[1]) * 10 + intval($latestMatch[2])) 
+                - (intval($curMatch[1]) * 10 + intval($curMatch[2]));
+        
+        // Pick icon and tooltip msg
+        $bg = "/css/images/";
+        $msg = "";
+        $link = "<a href='http://apt.sourcefabric.org/misc/'>" . $latest . "</a>";
+        if(($diff == 0 && $current == $latest) || $diff < 0) {
+            // current version is up to date
+            $bg .= "icon_uptodate.png";
+            $msg = "You are running the latest version";
+        } else if($diff <= 2) {
+            // 2 or less major versions back
+            $bg .= "icon_update.png";
+            $msg = "New version available: " . $link;
+        } else if($diff == 3) {
+            // 3 major versions back
+            $bg .= "icon_update2.png";
+            $msg = "This version will soon be obsolete.<br/>Please upgrade to " . $link;
+        } else {
+            // more than 3 major versions back
+            $bg .= "icon_outdated.png";
+            $msg = "This version is no longer supported.<br/>Please upgrade to " . $link;
+        }
+        
+        $result = "<div id='version_message' style='display:none'>" . $msg . "</div>"
+                . "<div id='version_current' style='display:none'>" . $current . "</div>"
+                . "<div id='version_icon' style='background-image: url(" . $bg . ");'></div>";
+        return $result;
+    }
+}