"Vette pech" (fat chance) appears to offend some of our users. The translations for these seem to vary wildly:
* dr: "pas de chance" (no luck)
* de: "Tut uns leid" (we are sorry)
* it, da,... : this part is left out. This is the best option in my opinion.

Add a method to SimpleSAMLphp_SessionHandlerPHP to restore a session existing previously to our own session. This can be used in SimpleSAML_Session to restore the PHP session status previous to calling our API, while also guaranteeing that our session is correctly saved. The documentation has been updated to reflect this and recommend how to deal with conflicting PHP sessions. This closes #244 and resolves #349.

Bugfixes: the PHP session handler only fetches the cookie configuration parameters if session_id() returns a non-empty ID. This won't happen if the application initialized a session previously, hijacking the session and causing all kinds of trouble. Instead, we need to detect if there's an active session, save its parameters and close it. After closing it, we can name a new session and set the cookie parameters.

Bugfix: when using PHP sessions, if there's already a session, session_id() will return the identifier of that session, not our session. In that case, we need to make sure it is our session so that we don't hijack the one of the application.

Resolve #359. The login button was disappearing in mobile devices. Reordered the form a bit too for those devices, so that the view is better.

Fixes: Mar 25 11:06:53 simplesamlphp INFO [0015a148dc] Template: Looking up [{login:processing]: not translated at all.

The login-page would not verify as valid XHTML 1.0 Transitional

Use stable versions of the modules to make sure no bugs can be introduced while further developing them.

Avoid the PHP session handler to generate errors when we try to retrieve a session after the headers being sent to the browser.

Bugfix: if an optional configuration is missing, we shouldn't register it to reuse it later (i.e. loading a config file as optional first and as mandatory later would make the second call to work -while it shouldn't-, since an empty config was loaded during the first call).

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