Update to OSGi 5 and Jetty 8 (#703).

Several 3rd-party components are updated.
Now we have a Jetty 8, that means Servlet API 3.0
And now we have Felix 4.4, that means OSGi 5

The details:

Felix HTTP Jetty 2.2.0 -> 2.3.0
    Jetty 7.6.13 -> Jetty 8.1.14
        Servlet API 2.5 -> Servlet API 3.0

Pax Runner 1.7.5 -> 1.8.6
    Felix 3.2.2 -> Felix 4.4.1
        OSGi 4.2 -> OSGi 5

Felix Configuration Admin 1.2.8 -> 1.8.0
Felix EventAdmin 1.2.12 -> 1.4.0

See #703.
Core: fix access to bundle root resource (#703).

The Webclient is functional again.

See #703.
Core: replace Felix HTTP by Pax Web (#448).

Felix HTTP Jetty is now replaced by Pax Web once and for all (hopefully).

We have Pax Web 3.1.2 with a Jetty 8 (that means Servlet API 3.0).

Also we have Felix 4.4 (that means OSGi 5) now (see #703).

We're still on JDK 6.

DM with Pax Web can be tested on the "pax-web-3" branch.
This is merged into master soon and will be part of the upcoming DM 4.4 release.

See #448.
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.