Configure application wide `Clock`

[smcvb]

Description

Although in a lot of cases, the positioning of the Clock on the GenericEventMessage as a public static field has been sufficient, as far as configuration goes, it is not very nice.

Granted, it can be adjusted by the user, since the field is public. But given the existence of the Configurer it is somewhat of an oddball in Axon Framework.

Hence, we should provide a means to define a single Clock on the overall Axon Framework configuration API.