[Rock-dev] Update to master/next/stable

[Sylvain Joyeux]

I've created two pull requests, which will obviously need some testing
... If anyone is interested.

This is basically the option 3 described here:
  http://rock.opendfki.de/wiki/WikiStart/OngoingWork/RockFlavorsOrReleases/How

https://github.com/rock-core/package_set/pull/12
  - makes 'stable' track the rock1408 branch
  - makes 'next' an alias for 'stable' (for backward compatibility reasons)

https://github.com/rock-core/rock-package_set/pull/19
  - updates the rock package set accordingly

TODO:
 - update the post-commit hook to warn people who commit on the stable branch

DIFFERENCES WITH THE ROCK1408 BRANCH
-----------------------------------------------------------------------
I've NOT moved any packages from master to stable (unlike rock1408
which moved all master packages to stable). If these PRs get accepted
into the package set, I'll announce on rock-users that maintainers
will have to request it explicitly. Two exceptions:
base/orogen/interfaces and drivers/velodyne_lidar as they were
dependencies of "released packages".

The non-Rock-branched packages are NOT pinned to a particular commit.
The PR contain the setup code for it, but I need to backport an
autoproj patch to make it work (will do it ASAP).

People using 'stable' will get switched to the new release next time
we release anything. What I want is that we've ironed out the release
process by then and "pin" them transparently before we release.

Sylvain