Draft templates for sl6.x-x86_64

Here are some fresh templates generated from the SL6x comps.xml file for the Yum based SPMA.

Apart from not having the package versions and architectures, the main differences are:
   - the 4 package levels are kept separate
   - the "mandatory" level is used as default
   - the language support templates are also separated
   - the "conditional" level has conditional statements

If all this seems like a good starting point for new sites, it should probably be merged into a new branch called "sl6.x-x86_64" which I don't have the privileges to create.

Also if someone has a better form for the "conditional" templates, please let me know.