Those using this new Menu class can easily generate a menu suitable for the menu template, and add new items. The Menu class calls an "adminmenu" hook as well for those modules willing to extend the menu.

It's divided in three main pages, as the old interface: front/configuration, authentication/testing and federation. For now, only the front/configuration page is working.

We'll use it in the new admin interface. For now, we just fix the old hook so that translations work for strings stored in dictionaries in the hooking module.

Create a new "configpage" hook for those modules that need to inject anything in the configuration page.

This allows us to change the signature of the hook, so that we pass it the \SimpleSAML\XHTML\Template object and then the hook can not only add data to be passed to the twig template, but also add its own translation domain. This was needed because many modules were putting their translations inside "core", and when moving those to the modules themselves, the new translation system cannot perform the translation because only the translations for the current module in use are loaded (in the config page, that's the core module). Therefore, we needed a way to get the Localization instance from the template, and a way to pass that to the hook so that the hook can register the translations for its own module.

It does not seem like something that is normal so a warning seems in
place. However, forbidding it does not add much value since we accept
unsollicited responses (from any idp) anyway.

Closes: #975

Change documentation from recommending 2048 bit keys to using 3072 bit
keys.

Given that we're recommending people generate ten-year keys, 2048 bit
keys are probably a bit short. Almost all commercial certificate
authorities now recommend 4096 bit keys, and eduGAIN requires 3072 bit
keys for new federations.

This change aligns the SimpleSAMLphp documentation with the lower
eduGAIN requirement, since that still meets most standards bodies
recommendations for 2028 (ten years from now). cf
https://www.keylength.com/

Closes: #177

Remove last use of experience icons theme so we can remove it after the old templates have been removed.

Extend @mapgrady's patch for simplesamlphp/simplesamlphp#498 to allow Scoping to be disabled on a per-idp basis as well as globally