Galleria template with image title and GPS position

These changes are some small improvements on the galleria template. The one moving title infos to the layer is only a matter of taste.

The UserComment exif data is not the best defined thing in the world... we can face some weird values depending on the image editor.
This can be simplified: `return any(image.hasLocation() for image in self.images)`

For the sake of consistency and pep8 respect, could you also change the function names to lowercase with words separated by underscores ? `has_location`, `show_map`.