Activate GUI for watermark layout.

It is now possible to layout properly a watermark whose scale is
computed based on the larger or smaller border. This make it possible
to use a watermark inside a style an apply it into images in portrait
and landscape mode with proper layout.
Upgraded and reviewed Spanish translation

 I have fully reviewed the Spanish translation, fixing typos,
 improving grammar and the language used.
Fix: snapshot + gnd, cliping, ... #9329
usermanual: add missing file lighttable_directory.png
don't crash on malformatted TIFF file

In case a file was alraedy rejected by GraphicsMagick, it's not a good
idea to try open it with our handmade imageio routines like TIFFOpen().
Let's take GraphicsMagick as a last resort if available.
If node stEvt:softwareAgent not found, skip as not a lightroom xmp.
Proactive fix to avoid a crash trying to dereference a null pointer.
Merge branch 'fix-crash-lr-import'

* fix-crash-lr-import:
  Proactive fix to avoid a crash trying to dereference a null pointer.
  If node stEvt:softwareAgent not found, skip as not a lightroom xmp.
adobe_coeff: Nikon Coolpix A same as D7000
white balance: make it relative to daylight balance

assuming that has been created wrt CIE daylight.

the end result is somewhat similar to ufraw, numbers vary wildly
but in principle it's relative to something constant and not to
camera white balance anymore.

also removed second temperature slider.
bauhaus: also reset to default on double click if -1 entry was selected.
Merge branch 'watermark-layout-options'

* watermark-layout-options:
  Activate GUI for watermark layout.
Update french translation.
whitebalance: default temperature is daylight wb
allow zoom under the "fit to screen" limit
smaller zoom steps under "fit to screen"
Merge pull request #208 from darktable-org/gnd_fix

Gnd fix
Make docbook valid

Fixed invalid docbook syntax especially the "id" attribute of the
elements where the attribute was with more than one word combined the
words with '_" so they will be easy to read.

Add declaration when necessary so document is valid by itself

Fix all documents so they are docbook valid.

Use <section> in favor of all other sect variants, since this makes
moving the sections easier

Signed-off-by: madanyang <toganm@opensuse.org>
Docbook5

Initial checkin for converting the usermanual to docbook5.

The layouts can change so better do not clone this branch, but wait
till it is merged into develop branch
Layout

Work on alernative layouts:

topics is for version 5.1 of docbook for assemblies
layout is for current docbook which is 5.0
darktable-v5.xml is a temporal document for this phase