Make compatible to contao 3.
Merge pull request #86 from tristanlins/hotfix-contao3

Contao 3 compatibility
Optimize css for checkbox wizards
Change the datepicker icon path for contao 3
added this at line 245

            if (!$this->columnFields)
            {
                continue;
            }

From time to time $this->columnFields ist NULL
Support the Contao 3 fileTree widget in columns
Pass field name to fileTree widget
Fixed DCA helper
Can't use a reference
Added new class to autoload.php
Input is cached, need to create a virtual field
Trying to satisfy Psi
Merge pull request #89 from kmielke/master

error in foreach if columnFields is null
Remove usage of deprecated injectBefore/injectAfter.
Update minified js files.
fix js error when Stylect is not defined
whitespace
use be script in fe, tested with some simple use cases (insteadof dont
working at all)
Merge remote-tracking branch 'origin/master' into dev
Merge remote-tracking branch 'backbone87/master' into dev