Add optional ability to load/save image rank property from/to xmp
sidecar "xmp.Rating" and color property from xmp "xmp.Label" ignoring
the ones provided in the processing params file.
This behavior is disabled by default and an option under settings ->
file browser has been added to enable it.
When enabled:
* On load:
* rank and color are not read from processing params.
* rank is mapped from xmp sidecar file rating entry.
* color is mapped from xmp sidecar file label entry.
* On save:
* rank and color are saved to the xmp sidecar
* rank and color are also saved to the processing param (pp3) files to
keep them in sync
Rating mapping:
Since rating can be also -1 but rank only goes from 0 to 5, the -1 value
is ignored like already done when importing from embedded xmp data.
Color mapping:
XMP has no color concept, usually programs like digikam uses the label
field to write a color name ("Red", "Orange"). The problem is that this
isn't standardized and label can be any string. Additionally Rawtherapee
has 5 specific colors while other programs can have different colors
with different name so they won't be shown if they don't map to the 5
color names supported by rawtherapee. On save only the 5 color supported
by rawtherapee wil be saved.
Trash is kept only in the profile files for multiple reasons:
* There's no trash concept in xmp, there's the rejected concept assigned
to a rating == -1.
* We could map rejected to trash but in rawtherapee rank and trash are two different values and
an image can have both rank >= 0 and trashed set to true.
Using an unique value like rating for rank and trash (when -1) will
require changing the current rawtherapee logic.
* Also digikam only handles ratings from 0 to 5 (no -1) and handles
trash in its own internal way without reflecting it in the xmp
sidecar.
The various Datum classes no longer have the toLong method and must be
replaced with toInt64.
ErrorCode is an enum class instead of an enum.
Error classes are reduced to Exiv2::Error.
This is mandatory (according to http://dpfmanager.org), and in fact needed for
Photoshop compatibility
(cherry picked from commit 5d281810cc7a7f7dc563dde030cf90c78dbf55d0)
