Improving error message if an output and an input type name are in conflict

[moufmouf]

The error message will now be:

For parameter $inAndOut, in TheCodingMachine\GraphQLite\Fixtures\InputOutputNameConflict\Controllers\InAndOutController::testInAndOut, type "InAndOut" must be an input type (if you declared an input type with the name "InAndOut", make sure that there are no output type with the same name as this is forbidden by the GraphQL spec).

See #188