Make sure style is always initialized.

Possible use of uninitialized variable found while reading code.
Do not rotate data upon loading. We will rotate it later in flip IOP
Refactor bitwise orientation into enum dt_image_orientation_t
IOP Flip: take care of flipping
IOP Flip: legacy params

<hanatos> okay, so the order of operations is: raw swap, raw flip, user swap, user flip
<hanatos> and we'll get
<hanatos> combined swap, combined flip
<hanatos> right?
<hanatos> so swap should just be xor, flipping twice is like not flipping
<hanatos> and we should swap the raw flip bits in case user swap was set for that axis
<hanatos> and xor that to the user flip
<hanatos> you're deciding whether or not to swap the flip bits based on the raw swap, not on the user swap
Refactor code that merges 2 orientations as a function
UNTESTED! Fix conversion of legacy_flip.user_flip with merge_two_orientations.
Correct comment for dt_image_orientation
Update French translation.

Thanks to Michel Leblond.

For #10002.
Fix thubmnails when using embedded jpg thumbs in lt mode
Focus detection: no need to care about rotation
Fix FD for portrait images just after "history stack" -> "discard"
dt_image_altered: just use `if'
Update French translation.

Thanks to Michel Leblond.

For #10002.
dt_dev_distort_{transform,backtransform}_plus: only check for piece->enabled, not module->enabled

WARNING: this might cause some regressions because i have not tested this extensively!
pixelpipe: better status differentiation rather than only a dirty flag
Merge pull request #616 from upegelow/pixelpipe_status

pixelpipe: better status differentiation rather than only a dirty flag
Updated Catalan translation
Merge pull request #617 from josepvm/master

Updated Catalan translation
usermanual: fix for #10009