liberalised version of Symfony Event Dispatcher

Refactored the code into the existing document class, to prevent introducing the complexity of two document types.
Moved the document class into a subfolder, updated all references
Added / updated unittests

Conflicts:
	library/Solarium/QueryType/Update/RequestBuilder.php

Conflicts:
	library/Solarium/QueryType/Select/Query/Component/Spellcheck.php

Tweaked readme file

- added some small fixes
- added unittests

Conflicts:
	library/Solarium/Exception/HttpException.php

Add body to HttpException (if available). Bad Request 400 is simply not sufficient to debug problems

Update composer.json