Add the ability to enable / disable and check for the editable property of a rendering engine. Implement for all three backends and extend the sample, document and unit test.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/SOC2011_WEBVIEW@68193 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/webview_webkit.cpp

@@ -702,6 +702,16 @@ bool wxWebViewWebKit::IsBusy()
      */
 }
 
+void wxWebViewWebKit::SetEditable(bool enable)
+{
+    webkit_web_view_set_editable(WEBKIT_WEB_VIEW(web_view), enable);
+}
+
+bool wxWebViewWebKit::IsEditable()
+{
+    return webkit_web_view_get_editable(WEBKIT_WEB_VIEW(web_view));
+}
+
 // static
 wxVisualAttributes
 wxWebViewWebKit::GetClassDefaultAttributes(wxWindowVariant WXUNUSED(variant))