rename PHPCRTypeGuesser to PhpcrOdmTypeGuesser

fix #155

i propose to use PhpcrOdmTypeGuesser as PHPCRODMTypeGuesser would look horrible, and its consistent with https://github.com/doctrine/DoctrinePHPCRBundle/blob/master/Form/ChoiceList/PhpcrOdmQueryBuilderLoader.php for example. (though admittedly there are some classes starting with PHPCRODM)

while looking at this, i noticed https://github.com/doctrine/DoctrinePHPCRBundle/blob/master/Form/DoctrinePHPCRExtension.php . i fixed a BC break in the type guesser that started requiring the assoc options. DoctrinePHPCRExtension is never used anywhere, and there is no service for it. what is it good for? it seems not needed for the form layer to work: https://github.com/doctrine/DoctrinePHPCRBundle/blob/master/Tests/Functional/Form/PHPCRTypeGuesserTest.php