Exposure IOP: disable Deflicker for 1.6 release
It is not fully ready.

The exact problem: calculated exposure compensation for same params
(target level and percentile) differs between my deflicker implementation
and "reference implementation" (ML deflick.mo)

Fix *will* alter computation results(computed exposure), and that is accepteble
only for something that was not released yet.

This does not break old (1.5) history stacks.

!!! TO BE REVERTED ONCE 1.6 IS RELEASED !!!
Merge pull request #695 from LebedevRI/disable-deflicker-for-1.6

Exposure IOP: disable Deflicker for 1.6 release
usermanual: reflect recent changes to the exposure module
usermanual: fix for #10148
usermanual: some more details on color zones
usermanual: more on the concepts of pixelpipe, module order and history stack
Merge branch 'master' of https://github.com/darktable-org/darktable
Update French translation of the usermanual after the issue #10148 has been updated by Ulrich Pegelow