remove most mentions to gitorious and even more ancient pre-Rock days

This commit migrates all links and manifest examples to use
github's package sets, as well as remove pre-Rock examples (rise and
rubim ... oh my god)
autoproj: the autoproj_bootstrap script  generated by rake dist:bootstrap is in bin/
contributing has its own section now
packages: update the package_structure document

The main update is the inclusion of all the categories we have
nowadays
ros: call aup before amake

While autoproj should checkout all packages properly, it is by far
the most robust mode of operation
ros: remove mention of gitorious_server_configuration

gitorious and github are properly setup in all rock installations nowadays
Merge pull request #15 from rock-core/update_to_modern_rock_workflow

Update to modern rock workflow