add apt repo examples to conf stub

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
sources_list help can take a filename now

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
add repo install to debian

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>