Remove language selection from the general configuration

refs #6073
Update preference form so that it suits the new language negotiation

refs #6073
Update web bootstrapping to suit the new localization procedure

Icinga\Application\Web::setupInternationalization now sets up the locale
from the current session first, if any, and falls back to the one from the
user's preferences, if any.

refs #6073
Redirect to /setup if necessary

A user gets now redirected to /setup in case he is not logged in, the token
file exists and no config.ini was found.

refs #7163
Add Cli command to generate and show setup tokens

One is now able to utilize `icingacli setup (show/generate)Token`

refs #7163
Re-add TokenValidator

refs #7163
Fix autosubmit of Icinga\Form\Config\General\LoggingConfigForm
Add method set/getByRef to Icinga\Web\Session\SessionNamespace
Fix value invalidation in Icinga\Web\Session\SessionNamespace
Write session on response

There should not be any necessity to write the session once changes are
being made to it. We now track whether changes were made and write
the session when responding to the user's request if so.
Remove method write() from Icinga\Web\Session\SessionNamespace
Add tests for hasChanged, set/getByRef and fix setByRef
Fix persisting notification messages in the session
Add Wizard

This is a container/controller for form based wizards. Can be used directly
or by using a subclass that allows for a more customized handling.

refs #7163
Make isValid* calls of configuration forms being static

This allows a more flexible usage as there is no need to access instance
formdata when validating such configuration.
Let the form decide where to get the resource configuration from

refs #7163
Add some redundancy to get more implicitness

Although this commit does not seem reasonable
at first the "big" picture proves its necessity!

refs #7163
Make the loglevel ERROR being the default

refs #7163
Make it possible to retrieve a list of available users for authentication

refs #7163
Add some more platform related calls

refs #7163