Allow to pass objects to ItemConverter instances

Remove type hint from in Workflow::filterItem

Remove type hint from in Workflow::convertItem

Remove typehint from WriterInterface
Remove useless $orginalItem from WriterInterface and fixed the phpdoc in WriterInterface
Added testcase for objects
Add is_array check to Workflow class
Add is_array check to Workflow class
Merge remote-tracking branch 'origin/object-in-itemconverters' into object-in-itemconverters

Conflicts:
	tests/Ddeboer/DataImport/Tests/WorkflowTest.php
Merge pull request #31 from Baachi/object-in-itemconverters

Allow to pass objects to ItemConverter instances