Add start() and stop() methods for unboundid.EmbeddedLdapServer

[etrandafir93]

As discussed in #1000, we should add start() and stop() methods for unboundid.EmbeddedLdapServer. As agreed, we should avoid throwing checked exceptions from these new methods, and implement the AutoClosable interface.

Opened poince:

• if we add the stop() method that will delegate to directoryServer.shutDown(true), should we deprecate EmbeddedLdapServer::shutdown ?