Simpler labels in Form->input

Let each application specify it's labels' classes if needed
$validate attribute declaration moved

$validate attribute moved to __construct() function to be always
available for each Document Object
Changed import url of the icons images

Path was changed to be able to import the image file in applications
that use an alias in the URL
Bootstrap 3 integration + bug fixes

Bootstrap 3 integration : alert-error class -> alert-danger
Bug fix : user id is sent to DocumentedBehavior to be saved on file
creation, if no user
Bug fix : custom function getHeaders in case the server does not run
APACHE