Fix with django 1.3

Hello,

I eventually managed to identify the incompatibility between helios and django 1.3 (see [1]). My proposed fix is to rename the "auth" application into "helios_auth". It is backward compatible. The commit messages should be self-explanatory.

  [1]: http://groups.google.com/group/helios-voting/browse_thread/thread/7b55f16e77f98565

I've tested interactively the result (by browsing): creating elections, trustees, etc. and no obvious regressions can be seen. The tests don't work for me (even before my changes and with django 1.2)... I haven't investigated this point.

Best regards,

-- 
Stéphane