Merge pull request #423 from hean01/master

Deprecated and remove the "backup" functionality of camera import.
write exif data to image before raising the temporary image signal

this fixes bug 9756
Only write the history stack when called from the darkroom.

Indeed there is nothing to save when called from the lighttable
and actually this will erase current history stack of the
selected images.

Better fix for #9340.
imageio: true should be TRUE

this fixes 0d874257deed1469316fe770611e32a989db680c
related to bug #9756
Fix handling of negative numbers.

This was preventing the capture module to create the film roll. The
initial value for the film roll is -1, and in this case the module
was creating a new capture film roll. But this bug was returning
a conf value of -1 as 0.
lua : fix crash or deadlock when leaving DT while lua is running
add storage and storage_param to dt_imageio_export

these are set to NULL where they don't make sense.
The point is to pass them to the signal to be caught by lua
lua: export storage and format as extra parameters to the intermediate file event
shadows&highlights revamped

main improvement is elimination of clamping where possible - no clamping of the
module's input and no clamping of its output. this should help to solve two issues:

* prevents hue banding when working on images with very high color saturation
* highlight reduction now also works on out-of-bound highlights

minor changes: lower memory usage in CPU codepath; better numerical stability on GPU.

legacy history stacks work as before - in order to switch to the new algorithm for
them you need to reset the module.
Update French translation.
gtkrc: also parse it for bauhaus widget size.