New Plugin LabCurves and plugin updates

[roland65]

Hi there,

I added today a new plugin called LabCurves. It does the same thing as the former plugin from Thomas Baruchel (see this thread http://forum.corel.com/EN/viewtopic.php?f=96&t=47017 for a discussion), i.e. when enabled it allows to manipulate the image curves in Lab space.
(For some reason, there was already a "phantom" plugin with the same name, so I had to enter the name "LabCurves2" in the plugin directory, but this has no impact and the true name is "LabCurves" as expected).

I also renamed the Scontrast plugin, who becomes LabTools. The new version should also be faster.
And at last, I updated the AutoLevels and USM plugins (code update, no functional change).

Have a nice day,
RB