Don't set shells as default whenever enabled

Because alternative shells like Zsh are almost non-functional unless
"enabled", it doesn't make sense to try setting them as default just
because they are enabled.
add mathematica-9.0.1
Build numpy against openblas
Don't set a default version of Mathematica

Nixpkgs should not set a default version of Mathematica. Many users of
Mathematica have institutional licenses and do not have immediate access
to new versions. If there is a default version in Nixpkgs, updating that
version will cause trouble for all such users.
networkmanager: load modules required for PPTP
Don't set shells as default whenever enabled

Because alternative shells like Zsh are almost non-functional unless
"enabled", it doesn't make sense to try setting them as default just
because they are enabled.
add mathematica-9.0.1
Build numpy against openblas
Don't set a default version of Mathematica

Nixpkgs should not set a default version of Mathematica. Many users of
Mathematica have institutional licenses and do not have immediate access
to new versions. If there is a default version in Nixpkgs, updating that
version will cause trouble for all such users.
Merge branch 'default-shell' of github.com:ttuegel/nixpkgs into default-shell
Merge branch 'mathematica' of github.com:ttuegel/nixpkgs into mathematica
Merge branch 'arpack' into installed-next
Merge branch 'default-shell' into installed-next
Merge branch 'keepassx' into installed-next
Merge branch 'mathematica' into installed-next
Merge branch 'networkmanager' into installed-next
Merge branch 'vobsub2srt' into installed-next
Merge branch 'installed' of github.com:ttuegel/nixpkgs into installed