Add RunScript and implement on all backends. Document and add a very simple unit test.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/SOC2011_WEBVIEW@68275 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/webview.h

@@ -262,6 +262,11 @@ public:
     */
     virtual void Reload(wxWebViewReloadFlags flags = wxWEB_VIEW_RELOAD_DEFAULT) = 0;
     
+    /**
+        Runs the given javascript code. 
+    */
+    virtual void RunScript(const wxString& javascript) = 0;
+    
     /**
         Set the editable property of the web control. Enabling allows the user
         to edit the page even if the @c contenteditable attribute is not set.