add file picking for osx and ios and implement equirectangular import

engine/app_events.cpp

@@ -22,6 +22,7 @@ void App::showKeyboard()
     LOG("show keyboard");
     redraw = true;
 #ifdef __IOS__
+    [ios_view registerForKeyboardNotifications];
     [ios_view becomeFirstResponder];
 #elif __ANDROID__
     displayKeyboard(and_app, true);
@@ -34,11 +35,25 @@ void App::hideKeyboard()
     redraw = true;
 #ifdef __IOS__
     [ios_view resignFirstResponder];
+    [ios_view unregisterForKeyboardNotifications];
 #elif __ANDROID__
     displayKeyboard(and_app, false);
 #endif
 }
 
+void App::pick_image(std::function<void(std::string path)> callback)
+{
+    redraw = true;
+#ifdef __IOS__
+    [ios_view pick_photo:callback];
+#elif __OSX__
+    std::string path = [osx_view pick_file];
+    callback(path);
+#elif __ANDROID__
+    //displayKeyboard(and_app, false);
+#endif
+}
+
 bool App::mouse_down(int button, float x, float y, float pressure, kEventSource source)
 {
     redraw = true;