added ability to watch is file changed wile server is running

lib/server/appcache.js

@@ -0,0 +1,58 @@
+var fs = require('fs');
+
+/* varible contain all watched file names
+ * {name: true}
+ */
+var FileNames = {};
+var i=0;
+
+/* function thet use for crossplatform
+ * access to fs.watch or fs.watchFile function
+ */
+var fs_watch = null;
+var on_fs_watch =null;
+
+setWatachFunctions();
+
+function setWatachFunctions(){
+    if(process.platform === 'win32'){
+        /* good on windows  */
+        fs_watch    = fs.watch;
+        on_fs_watch = onWatch;
+    }        
+    else{
+        /* good on linux    */
+        fs_watch    = fs.watchFile;
+        on_fs_watch = onWatchFile;
+    }
+
+}
+
+exports.watch = function(pFileName){
+    console.log(pFileName + ' is watched');
+    
+    if(!FileNames[pFileName]){
+        try{
+            fs_watch(pFileName, on_fs_watch(pFileName));
+        }
+        catch(pError){
+            console.log(pError);
+        }
+        
+        FileNames[pFileName] = true;
+    }
+};
+
+function onWatch (pFileName){
+    return function(pEvent, pFileName){
+        console.log('file ' + pFileName + 'is changed');
+    };
+}
+
+function onWatchFile(pFileName){
+    return function(pCurr, pPrev){
+        console.log(pCurr);
+        if(pCurr.mtime !== pCurr.pPrev.mtime)
+            console.log('file ' + pFileName + 'is changed');
+    };
+}