Updated translations from transifex.
check if file exists before using getimagesize()
fix code style
Merge pull request #628 from Zeromax/fix-toolbox-fileexists

[tng] ToolboxFile should check if the file exists.
Add php 5.6 to .travis.yml
Add Contao 3.4 to allowed failures as it is in beta state.
Work around the fact that Contao\Database::getInstance() always creates an instance.

Contao\Database::getInstance() always creates an instance, even when no
driver is configured.
Therefore we must check that the Db is configured properly.
Cleanup uses in class BackendIntegration\Boot.
Fix issue #627 - Event dispatcher was not passed to DrawSetting::modelToLabelDefault().
Fix code style issues in Item.php
Refactor Item::isArrayEmpty() to reduce complexity.
Fix type cast code style errors (code style was changed).
Fix phpDocs.
Properly return css class.
Wrap long line.
Refactor DCA handler classes for tl_module and tl_content into base class.

Reducing copy paste occurences.
Add missing return.
Use unserialize() where appropriate.
Add unit tests for constructors of MetaModel and Base attribute.
Update MetaModel.php

Fixed check if varValue is an array