Simplify context setup, set properties on the global object directly instead of using templates

include/AdblockPlus/JsEngine.h

 #ifndef ADBLOCKPLUS_JS_ENGINE_H
 #define ADBLOCKPLUS_JS_ENGINE_H
 
 #include <stdexcept>
 #include <string>
 #include <v8.h>
 #include <AdblockPlus/JsValue.h>
 
 namespace AdblockPlus
 {
@@ skipping 25 matching lines @@
     JsValuePtr NewValue(bool val);
     inline JsValuePtr NewValue(const char* val)
     {
       return NewValue(std::string(val));
     }
     inline JsValuePtr NewValue(int val)
     {
       return NewValue(static_cast<int64_t>(val));
     }
     JsValuePtr NewObject();
+    JsValuePtr NewCallback(v8::InvocationCallback callback);
     static JsEngine& FromArguments(const v8::Arguments& arguments);
     JsValueList ConvertArguments(const v8::Arguments& arguments);
 
     inline FileSystem& GetFileSystem()
     {
       return fileSystem;
     }
     inline WebRequest& GetWebRequest()
     {
       return webRequest;
@@ skipping 18 matching lines @@
   private:
     FileSystem& fileSystem;
     WebRequest& webRequest;
     ErrorCallback& errorCallback;
     v8::Isolate* isolate;
     v8::Persistent<v8::Context> context;
   };
 }
 
 #endif