User-visible changes:
--------------------
Added a --from option for autoproj update and autoproj status, that
allows to update an installation from another installation. For
instance:

# Compare the current install from another rock installation
autoproj status --from=../toolchain-devel
# Update the local install from another rock installation
aup --from=../toolchain-devel

Made the interaction between metapackages and ignored packages configurable
The "new" behaviour in 1.9.x was to NOT generate an error if (1) a
metapackage depends on a package X and (2) X is excluded. This was
recursive (i.e. would ignore X and Y if metapackage depends on Y, Y
depends on X and X is excluded).
This is not the default behaviour anymore. It can still be
reactivated for "global" metapackages as e.g. 'rock' by setting the
weak_dependencies flag

Fixed MacPorts osdeps handling

Added the autoproj-show tool: display detailed information about packages
Among other things, it displays WHY a given package gets installed,
which allows to debug the "why in hell is package X installed ?"
question .

Added the autoproj-list tool: summary of known packages.

Support Ruby 2.0

The archive importer now autodetects when an archive is changed, and
asks whether the current checkout should be deleted.

Misc bugfixes