Merge pull request #48 from jouvin/sl6.x-misc

sl6.x: various package group added/adjusted
Add variable OS_BIND_CHROOTED to determine if bind-chroot must be installed
(false by default)
Add a rpms category to add Python 2.7 and related tools
Add missing dependency for Quattor development (unit tests)
rpms/editors.pan: add more Xemacs modules by default
document viewers category: add a2ps
Add a few more packages to development-base-tools category
Interactive server category: add mutt (mail client)
Merge pull request #50 from jouvin/sl6.x-rpms-cat

sl6.x rpms category adjustments
Add LICENSE information (Apache 2.0)
Merge pull request #54 from jouvin/sl6_license

Add LICENSE information (Apache 2.0)
sl6.x: add required dependencies for Quattor development
Merge pull request #57 from jouvin/sl6.x-quattor-dev

sl6.x: add required dependencies for Quattor development
Revert modifications from rpms/group/development (must match RH definition)
Add nedit to the list of standard editors
Add libXScrnSaver to interactive servers
rpms/development-base-tools: add python-devel and openmpi
rpms/document-viewers: add xdvik
Add rpms/virtualbox