Remove scripts/debian as it is maintained in Debian itself

http://anonscm.debian.org/gitweb/?p=debian-science/packages/yade.git
Remove extra/boost_python_len.hpp as it was for very old boost-versions.
Remove extra/foreach.hpp_local. Not used anywhere.
Remove site_scons. Forgotten during cmake-migration.
Remove convexHull2d. Was blocked.
Remove boost-python-indexing-suite-v2-noSymlinkHeaders.

Not used anywhere in the code.