And drop the separate ingredients search, while we are at it.

Fiddle with label char-widths, to get an unchanging width.

Mnemonics and accessible labels in some places.

Use a GdTaggedEntry for search, and add a popover next to it
which allows to add tags for the meal, dietary restrictions or
ingredients to include or avoid. This makes the plain search
entry perform a super-set of the separate ingredient search.

This will be used in the future for a more powerful search.

We are going to use a tagged entry for search in the future.

This was accidentally broken a while ago.

This reverts commit e6f9dedf.

We no longer need this, now that each image has a 'dark text'
boolean.

This lets us decide about dark or light text on a per-image
basis.

It is not used anymore.

With the expander, it doesn't make much sense to hide empty
categories.

This was an oversight when splitting the diets into two
containers.

Stick to 3 columns here as well, and center the content.

This follows what gnome-software is doing.

This is using the same trick as the cuisine page.

Stick to 3 columns here as well.

Stick to 3 columns, and center instead of reflowing.

Stick to just 3 picks per row, and make the categories
expand like they do in gnome-software.

This will be used for text thats overlayed on the image.
We may eventually have one color per image, but for now,
just use a single one.

Just because we can.

This is the same idea as seen in gnome-software.

These are just copied from gnome-software.

We'll use it as a fallback image in the future.

Rely on the child-activated signal of GtkFlowBox to make the
labels clickable as well.

This was done for everything already except for categories,
and their visibility now depends on the recipes in the store.

This can happen if you navigate through the cuisine page to
a recipe, then edit it to make it have a different cuisine,
and then go back.

This makes the file chooser properly anchored to the preferences dialog.