-fixed export templates not loading/exporting on Windows

-fixed TouchScreenButton with stretch2d
-fixed(?) OSX crash on startup (test!!)
-compilation fixes on windows
-CollisionPolygon editor works again
-find buttons en find dialog
-TileMap editor cleanup (removed "error", made nicer)
-viewport flicker fixed
-make .scn default extension for saving scenes
-export the rest of the network classes to gdscript

tools/editor/editor_import_export.cpp

@@ -471,6 +471,18 @@ Error EditorExportPlatform::export_project_files(EditorExportSaveFunction p_func
 		EditorImportExport::get_singleton()->image_export_get_images_in_group(E->get(),&atlas_images);
 		atlas_images.sort_custom<StringName::AlphCompare>();
 
+		for (List<StringName>::Element *F=atlas_images.front();F;) {
+
+			List<StringName>::Element *N=F->next();
+
+			if (!FileAccess::exists(F->get())) {
+				atlas_images.erase(F);
+			}
+
+			F=N;
+
+		}
+
 		if (atlas_images.size()<=1)
 			continue;
 
@@ -814,6 +826,13 @@ Error EditorExportPlatform::save_pack_file(void *p_userdata,const String& p_path
 	pd->file_ofs.push_back(td);
 	pd->f->store_64(0); //ofs
 	pd->f->store_64(0); //size
+	{
+		MD5_CTX ctx;
+		MD5Init(&ctx);
+		MD5Update(&ctx,(unsigned char*)p_data.ptr(),p_data.size());
+		MD5Final(&ctx);
+		pd->f->store_buffer(ctx.digest,16);
+	}
 	pd->ep->step("Storing File: "+p_path,2+p_file*100/p_total);
 	pd->count++;
 	pd->ftmp->store_buffer(p_data.ptr(),p_data.size());