redraw signal: simplify the locking logic somewhat.

and make it more responsive, i.e. don't forget redraws issued from the gui thread.
Update fr.po for last Lightroom support.
Kill may be used uninitialized warnings.
Add defensive code for whratio.
Another may be used uninitialized warning killed.
redraw: allow more redraws per second.

this makes dr mode less laggy.

maybe this is still the wrong place to do this, maybe import (main problem)
should just throttle the signal emission instead.
film: remove unneeded wrapper
film: only redraw once after import, not for every image.
redraw: remove now obsolete flood stopping.
Fix compilation error in previous commit.
do no longer autoapply dithering; modules needs to be activated by user

this avoids that images are marked as modified even if history stack
is purged
do nothing in dt_dev_read_history() if no modules are loaded

this avoids warnings like the following if history stack is discarded from within lighttable mode:
[dev_read_history] the module `sharpen' requested by image `IMG_7273.CR2' is not installed on this computer!
usermanual: small fix to allow inlinegraphics in levels doc
Create a unique index constraint for imgid/color for color_labels table.

This is a constraint that must be obeyed, nice to let SQLite a
chance to check.
opencl: make sure histogram is shown in tonecurve/levels module even if  preview runs on OpenCL
noise profile: another sony nex-5n, numbers are spot on :)
Minor code reorganisation.
Code refactoring to expose dt_ratings_apply_to_image.
Add support for importing rating from Lightroom XMP.
Merge pull request #173 from TurboGit/add-index-constraint

Create a unique index constraint for imgid/color for color_labels table.