Make the plain nginx version the same as nginx-ssl.
In a further change we will replace nginx by a dummy package,
depending on +nginx-ssl instead. This allows a smooth upgrade.

For nginx-util leave the ssl and the ssl-nopcre versions only.
For nginx-mod-luci remove the duplicate ssl version.
Replace the removed packages by dummies for a smooth upgrade.
The dummy packages will be removed after a transition period.

Additionally, enable the http2 module for nginx-ssl by default
and cleanup the nginx.init file.

Signed-off-by: Peter Stadler <peter.stadler@student.uibk.ac.at>

Instead of the default nginx.conf file this file is a small variant
without examples that enables the /etc/nginx/conf.d/ directory.

It will pull in all configuration files from the conf.d directory.
So, other packages can add their server parts in the conf.d directory
without modifying the main nginx.conf file (cf. #9860).

Changed also the default logging behavior:
	error_log stderr; # the init forwards it to logd
	access_log off;

See the updated documentation at:
https://openwrt.org/docs/guide-user/services/webserver/nginx

Signed-off-by: Peter Stadler <peter.stadler@student.uibk.ac.at>