Rename \SimpleSAML\Locale\Translate::getTranslation() to the more comprehensive \SimpleSAML\Locale\Translate::getPreferredTranslation().

Candidate for removal/rewrite

A template now has a translator-object, SimpleSAML_Locale_Translate.
This handles the existing translation system.

The translator has a language-object, SimpleSAML_Locale_Language. This
handles discovery and switching of locale.

SimpleSAML_XHTML_Template has several methods that are wrapped
translator-methods:

t()
isLanguageRTL()
getLanguageList()
getTranslation()

This way it isn't necessary to change much of the existing system.

This will invoke a more convenient on screen keyboard on mobile
devices and give some syntax validation as a bonus.

Try with "composer update" instead of "composer install". The latter does not support --prefer-lowest.

Since this branch is now officially released we need to support it.

* Remove 404 link to SSP news; this is covered on simplesamlphp.org now.
* Make screenshots link relative, so docs don't trigger insecure
  content warnings.
* Compress png images.

Fix/keep empty folders

Update translations to the latest changes registered in translation.rnd.feide.no. The portal is now down, so any new translations must come as pull requests.

(being respectful with occurences that might change the behaviour, i.e. default database prefixes)

This reverts commit 7a801334.