a new argument (`True` by default) fix orientation (i.e. rotate according to EXIF data) of
image when resizing it.
A new `fix_orientation` method (unused for now) let do it independently
/!\ new optional dependency: CairoSVG (with installed `[SVG]` extra)
- new `convert` method in `tools.image` to save an image in an other format, with support
for SVG (when CairoSVG is available)
- new `imageConvert` method is available for frontends
media type is guessed first from filename, then if it's not enough, the file is opened to
try to guess type. If it still can be determined, None is returned.
