IO: Removed InMemory handler
IO: de-duplicated services
IO: Added custom factory method for filesystem handler
IO: added EzPublishIOBundle with configuration

The "main" io handler service is now always used,
and is dynamically built depending on the semantic config.

The ezpublish_io.handler tag is added, with an alias property for the name of the handler.
IO: made filesystem the default handler
IO: Removed unused IO config parser