Rename Icinga\Web\Form\Decorator\BootstrapForm

We do not use bootstrap anymore but do not want the default Zend
decorators either so this decorator got a more common name.

refs #5525
Refactor Icinga\Web\Form

We eagerly waited badly for a new approach to build forms, so here it is.
Should be the best compromise between the Zend_Form functionality and
our requirements regarding automatic submits.

refs #5525
Adjust Icinga\Form\Authentication\LoginForm to suit the new form builder

refs #5525
Adjust Icinga\Form\Config\LoggingForm to suit the new form builder

refs #5525
Merge branch 'master' into bugfix/rebuild-form-builder-5525

Conflicts:
	application/forms/Authentication/LoginForm.php
	library/Icinga/Test/BaseTestCase.php
	library/Icinga/Web/Form.php
	library/Icinga/Web/Form/Decorator/BootstrapForm.php
Forms do not need a special title property

As our upcoming wizard has no menu and our tabs are hardcoded we do not
need a special "title" property anymore.

refs #5525
Form buttons need to be added explicitly

We either demand the user to add a submit button or provide a implicit
function call to be implemented by him, adding additional elements once
the form gets rendered.

refs #5525
Configuration values need to be inserted to forms explicitly

It's the controllers' responsibility to ensure that forms are populated with
configuration values on GET requests.

refs #5525
We only want to rely on Form::isValid() when about to process forms

As the new auto-submission implementation does not depend on whether
a submit button was pressed or not we need another way to determine
whether a form should be processed.

refs #5525
Rename initCsrfToken to addCsrfToken and move it upwards

Form::addCsrfToken() should be public and fluent to ensure more
flexibility.

refs #5525
Make form creation lazy and implement the new validation mechanism

Form creation must not depend on specific function calls. If a forms' elements are required and missing, create them. Form::isValid() must be
able to determine whether a form can be processed or not without to rely
on a particular button value.

refs #5525
We cannot know what kind of data is passed to Form::isValid()

refs #5525
Also mention the viewscript functionality of Form::loadDefaultDecorators()

refs #5525
It's a form's responsibility how its submit button should look like

refs #5525
Adjust LoginForm to suit the "final" form builder implementation

refs #5525
Adjust LoggingForm to suit the "final" form builder implementation

refs #5525
Remove Icinga\Form\Install\LoggingPage
Do not consider disabled elements when checking form completion

Values of disabled inputs are not sent by browsers.

refs #5525
Adjust preferences form to suit the new form builder implementation

refs #5525
Adjust general config form to suit the new form builder implementation

refs #5525