EZP-21035: move isSingular() check back to BadStateException
EZP-21035: added ContentTypeValidationException
EZP-21035: move isSingular() check to ContentTypeValidationException and BadStateException
EZP-21035: update ContentType controller for added exceptions
EZP-21035: updated tests
EZP-21035: fix passing by reference warning
EZP-21035: updated REST specification
EZP-21035: updated 5.2 BC changes