Sometimes it is quite helpful to see the values the validator objects.
Especially when it is hard to comprehend why the validation fails if one has,
say, an image in a stale cache which the validator does not have.

The dependency was removed in f1cdbd834f5baf5db5c7d73849161b186a2d9c54
and 8c58e47632f1e3da2723e57b2cb1bf775da37234. Let's update docs accordingly.

The timestamp comes from a converted release date but it is in UTC. So anyone
east of UTC will get a "timestamp is in the future" warning for today's date
until UTC ticks past midnight.

According to Wikipedia the highest offset is UTC+14 so let's offset our time
by that much. This way we treat "today" as valid release date anywhere on the
planet.

Fixes https://github.com/hughsie/appstream-glib/issues/317

Fixes https://github.com/hughsie/appstream-glib/issues/312

Flathub is already patching appstream-glib to remove this check.

Fixes https://github.com/hughsie/appstream-glib/issues/302

Fixes some of https://github.com/hughsie/appstream-glib/issues/302

There's no obvious reason why we should restrict this in the generator.

The plan was to require <release> for validate, so that we would be able
to require a version number for flathub, but it accidentally got enabled
for validate-relax as well.

Signed-off-by: Richard Hughes <richard@hughsie.com>

 * Require <content_rating> for any desktop or console application
 * Make <release> mandatory when validating
 * Further relax style requirements
 * Require description for desktop an console apps

This changes a lot of things that are now best practice for all apps, and
required to be included in Flathub.

Use `appstream-util validate-relax` to ignore some new failures and use
`appstream-util validate-strict` to bring them back.

Fixes: https://github.com/hughsie/appstream-glib/issues/263