pom.xml: for correctness always force Java 8
tmfcore_war/pom.xml: fix jersey and jetty

It was wrong to declare jetty as a compile dependency because
we're using it as an external container (which could be replaced
for example by tomcat).

Change the jersey version to 2.7. This is arbitrary.

Also, do not use scope 'import' which was not the correct
thing to do in this context.
Commit web.xml as is

Next will follow a commit for cleaning it. We are not 100%
sure whether this stuff is needed later!
web.xml: update the way in which we expose servlets

This is consistent with the new specification of jax-rs.

While here, expose /* rather than /core/*.
Add changes to tmfcore