Some packages removed and cleaned up

In this release some packages are removed from the repository because we realized that they are easier to maintain outside - just like on the master branch. Futhermore, this branch has been stripped to the minimum required, including its Travis configuration.

91a2d3a 2017-04-11 Further simplify Travis configuration         ..ian Lindig
5785417 2017-04-11 Move rpc and shared-block-ring to packages/.. ..ian Lindig
3d2d9db 2017-04-11 Add back shared-block-ring to xs/             ..ian Lindig
3750a80 2017-04-11 Simplify .travis.yml                          ..ian Lindig
b2b0190 2017-04-11 Remove xapi-xenops                            ..ian Lindig
1272933 2017-04-11 Remove packages that become spec files        ..ian Lindig
dd3f571 2017-04-10 Add missing into_repo.sh for Travis builds    ..ian Lindig
cf34554 2017-04-10 Enable Travis builds                          ..ian Lindig