Make sure to pass all variables defining the proper python version as found by
robotpkg, otherwise ros CMakeFiles may happily find python-3.2 and use it
instead of python<3, although this does not work in the end (at least ros-rx
does this and breaks on F17).

This is done in the common ros Makefile as this affects all packages.

Factor out the following:
 - PKGNAME with ros- prefix. This is overrided for a few base pkgs only
 - MAINTAINER
 - LICENSE

These can still be overriden on a per pkg basis.

std_msgs contains common message types representing primitive data types and
other basic message constructs, such as multiarrays. For common, generic
robot-specific message types, please see common_msgs.

std_msgs contains wrappers for ROS primitive types, which are documented in the
msg specification. It also contains the Empty type, which is useful for sending
an empty signal.

This package also contains the "MultiArray" types, which can be useful for
storing sensor data.