[maven] Change the version number of the Guava artifacts.

The fork of the Guava library provided by the Janus project was updated
for depending on the version 4.0-beta4 of Guice (the one already used by
the Janus platform).

The Janus platform dependencies were updated for avoiding any conflict
in the versions on the included artifacts of Guice.

see #76

Signed-off-by: Stéphane Galland <galland@arakhne.org>
[injection] Avoid self injection of the context-space service.

Signed-off-by: Stéphane Galland <galland@arakhne.org>