Add the support for multiple agent

For this, a new field has been added to the register message, the domain
type. Agent object and agent application object have now a domain type
so we can enable/disable the right event for the right agent for a
client command or during an application registration.

The "jevent" name has been renamed to "aevent" so further remove the
concept of Java event.

Signed-off-by: David Goulet <dgoulet@efficios.com>