[#409] Update documentation of java examples.
[#409] Update documentation of java examples.

In this commit, only the documentation of the Java sender is updated
and points to the provided classes in the example module.

Signed-off-by: Karsten Frank <22534dcdeefa21bf02bac7694b065eeae56646bb@bosch-si.com>

dejanb/hono,dejanb/hono,dejanb/hono