add file picking for osx and ios and implement equirectangular import

engine/texture.cpp

@@ -82,6 +82,16 @@ bool Texture2D::load(std::string filename)
         return false;
     return create(img);
 }
+
+bool Texture2D::load_file(std::string filename)
+{
+    LOG("load texture %s", filename.c_str());
+    ui::Image img;
+    if (!img.load_file(filename))
+        return false;
+    return create(img);
+}
+
 void Texture2D::update(const uint8_t* data)
 {
     bind();