List of photos (gallery.list)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
One photo per line, tab-separated columns:

	File name (relative to OrigDir in config)
	Identifier (16 hex digits)
	Orientation: one of "l", "r", "d", "."
	Transformation -- sequence of:
		n	normalize contrast
		s	sharpen
		h	equalize histogram
	Title (UTF-8 string)

Lines starting with "#" are ignored.

Lines starting with a tab add further attributes to the previous photo.
The following attributes are recognized:

	lat		geographic latitude in degrees north of equator
	lon		geographic longitude in degrees east of Greenwich
	alt		geographic altitude in meters
	t		time when the photo was taken (2014-01-25 09:40:12)


Importing meta-data from other sources
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Occasionally, you want to add photos from a source which already provides
some meta-data. In this case, you can construct a gallery.list with a subset
of fields, or feed the stdin of "gal scan" with such a list.

For convenience, orientation, transformation and title can be also given
as named attributes. They are called "orientation", "xf", and "title".


Photo meta-data (PhotoDir/gallery.meta or CacheDir/cache.meta)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Perl Storable containing a single hash.

$meta->{photo}->{$identifier} is a hash of:
	o		orientation
	xf		transformation applied
	w		width after scaling
	h		height after scaling
	w0, h0		width and height of original image
	title		photo title
	fmt		photo format (png/jpg; defaults to jpg)
	lat		geographic latitude in degrees north of equator
	lon		geographic longitude in degrees east of Greenwich
	alt		geographic altitude in meters
	t		time when the photo was taken (2014-01-25 09:40:12)

The rest is present in cache.meta only:

$meta->{sequence} is an array of photo IDs as they appear in the gallery.

$meta->{thumb}->{$format}->{$identifier} is a hash of:
	w		thumbnail width
	h		thumbnail height