[KPhotoAlbum] Breaking changes in file layout

[Tobias Leupold]

Hi all, I'll join the discussion as well ;-)

> XDG_CACHE_DIR/kphotoalbum/<db>/.thumbnails/
> XDG_CACHE_DIR/kphotoalbum/<db>/.videoThumbnails/

Do you think the leading dot is needed (making the directory hidden)? We're
already in "kphotoalbum/" one leven below, so why not "thumbnails/" and
"videoThumbnails/"?

> I get your point, but I'm not a big fan of constructs like "/home/
> johannes/.cache/kphotoalbum/home/johannes/Pictures" either.

I personally would prefer the hash. Maybe we could add a file like
"collection" or such containing the path to index.xml for easier user-side
identification. I wouldn't add the whole path. If so, please at least don't
use pipe symbols to mask the slashes, that also have to be masked when using
the directory name ...

It's surely a good idea to have database-specific settings in index.xml. If we
do this, it's the time to change this.

Speaking of CategoryImages: To be honest, I also wondered why this seems to
work and no bug reports emerge. The implementation could be better.

This one could actually be hidden by a leading dot imo, like
"DBDIR/.CategoryImages/". Also, I think we need other file names. I would
organize the images in directories per category (atm we have category-
something.jpg, should be category/something.jpg, think of category renaming!).
Additionally, we need a better masking of non-alphanumerical characters, so
that e. g. "/" is a category isn't a problem (like a "%" followed by the
number we would use to define the character like in HTML's { or such?).

This rework would definitely be the time to fix/improve this.

Tobias