Pax Web fix: no session timeout (#448).

New config parameter in global pom.xml:
{{{
<org.ops4j.pax.web.session.timeout>0</org.ops4j.pax.web.session.timeout>
}}}

The amount in minutes when a session times out at server-side.
Set 0 for no time out.

Pending related Pax Web: HTTPS configuration.

See #448.