FC-69 Replace Remote Call with @Retryable and new Continuation implementation

Remote calls used SQS to distribute execution of command and query methods, as well as enable retrying of failed commands/queries. This causes subtle issues with failure scenarios, and problems with method call or response serialisation.
Remote calls have been replaced with equivalent functionality that does not use messaging (SQS). This change introduces new annotations, @Retryable @DeferResult and @ContinueResult. These support retries and continuations.

Signed-off-by: Steffan Westcott <steffan.westcott@clicktravel.com>
Spring AOP supports this alternative notation, where the type is indicated by the method parameter with the specified name. This is used where it is desired to pass in the annotation to the advice. It is needed here to provide access to the annotation parameter values.