NF: initial sketch for a script to enable NeuroDebian repo on any Debian/Ubuntu system

TODO: fetch/use information about mirrors
minor screw up fix
ENH: choose the best mirror using netselect and other enhancements
ENH: fixes + mimic nd_querycfg with a direct python query so could be used without neurodebian-devel installed
ENH: do not bother proceeding if config is the same already + enable sources based on apt-cache showsrc apt
ENH: removed all obsolete TODOs, fix execution around netselect, added doc on depends
BF: fetching/reporting of the config file
ENH: Allow to pass config via environment, install needed packages (if --install), env controlled mode to just do defuns
ENH: do not provide -D to netselect on older (squeeze) deployments
BF/ENH: if apt-get update fails because of us -- move our generated file aside
ENH: minor -- rename apt file into -failed.disabled (not .failed-disabled)

otherwise apt would still whine (just a warning though) about it having
an incorrect extension
ENH: use -I for netselect where available (ICMP is more likely to be allowed to reach than UDP)
Adding neurodebian and neurodebian-repository packages
ENH: initial debconf .config and few tune ups for that in the nd-aptenable
initial postinst and postrm scripts for neurodebian-repository pkg
BF: right -- we can't apt-get update while installing the package (via apt at least, assuming it to be default way)

+ various fixups
Move keyring into Depends for repository since we do not apt-get update anyways
some notes + adding netselect into pre-depends of the neurodebian-repository
BF: Disable logic for demanding netselect (absent on ubuntus)

probably we could sophisticate it with all vendor-specific gizmos
http://raphaelhertzog.com/2010/09/27/different-dependencies-between-debian-and-ubuntu-but-common-source-package/
but it is just more reasonable to assume that netselect would eventually
come back
ENH: sketch for a test to check installation of the package