Merge pull request #52 from backbone87/master

fixes a double dollar sign typo and removes trailing whitespaces.
Fix typo
Moved DC_General.php to module folder and added stub loader php file for Contao 2.X.
This improves Contao 3 compatibility, as now the autoload generator will also find
the DC_General class.
Update DC_General.php

Fixed check for changes of the widget value
Add support for adding/removing buttons
Update sorting - Use the field sorting flag if exists, instead of the global sorting flag.
Add support for adding/removing buttons
Adding composer.json
Bugfix: make ajax calls work again after commit a8b6c826f61cc1640c92a091e050dae6c5a5dc71.
We MUST NOT reload automatically submitted post requests.
creating items in parent modes generates sorting value of 0, which
trumps the sorting calculation algorithmn, implement a rudimentary
foolprove way to establish an "append-to-the-end" sorting value and
calculate it for mode 4 creates, still needs to be done for other modes