Fix #16880: regression introduced by original patch
Fix #16880: another one
Fixes #16848: Remove main page from main menu when news feature is OFF

The main page was really designed to include the news which has been deprecated for a while. Hence, the main page is useless for most users. This change hides it unless the news feature is ON.

This is until the news feature is completely removed.
Prevent plugin pages access when upgrade pending

If a plugin's code has been upgraded, but the schema is still on the old
version, the plugin is effectively disabled (i.e. its entry points are
not displayed). However, it was still possible to access individual
pages directly, which could lead to errors.

This commit adds an extra check in plugin.php which triggers an error
when the plugin needs to be upgraded.

Fixes #16706
Fix group actions not sending notifications

Added missing email_generic() calls

Fixes #6343, #13659