This fixes default packet redirection when merging multiple re6st
networks. Nodes will then install multiple default routes for each re6st
network with the correspond src-prefix.

The changes include:

- redistribute default route with src prefix on gateways
- remove the now obsolete default option
- if subtrees is not available in the kernel, delete src prefix from
  the default route and don't advertise the default route to other
  nodes
- if there is no src prefix in the redistributed default route, add
  one to be retro-compatible with the old gateway behaviour

Implement select in multicast.py to fix immediate return causing 100% cpu load
See merge request !39

This reverts commit f9b112a7

python-unshare and python-passfd are dependencies of nemu: https://github.com/NightTsarina/nemu/blob/master/setup.py#L18,
but nemu in pypi: https://pypi.org/project/nemu/0.3.1/ is outdated, it has no dependency defined
so keep those here

This is required for 47f69a00
("redistribute default routes with src-prefix").

See merge request !38

For instance 89.30.119.100 has an entry in the geoip2 database without country
key

anyway, let test failed if any error

modify fixnemu device name comment, remove extra line, space, remove dup
definition, eek

Remove duplicate definitions of DEMO_DIR, and define it in the tests
module

This test create a real client and server, use client to call rpc.
Because not include re6stnet, babel_dump related functions aren't tested

see nexedi/re6stnet!38 (comment 161622)
for detail.

remove useless test, correct typo and eek problem, refactor verbose
command

see nexedi/re6stnet!38

Use the files in demo(dh, fixnemu), and auto create ca, cert, key file

nemu use "%.4x%.3x" % (os.getpid(), n) to generate device name, but it
define the min length not the max length, when pid is high, this will
exceed 16 bytes IFNAMSIZ

network_build: use nemu to create net namespace, provide several network

re6st_wrap: wrap the deploy of re6st node, ease the creation of cert
file and run of the node

test_net contain the tests:
  - ping test: net segment(router), multi-net segment(demo),test after a
    reboot. Because net_demo contain a subnet UPnP, test is not stable.

ping is like ping file in demo, a script to run multiping

registry: add test for RegistryServer and registryClient,
testRegistryServer mainly test methods concerned to http rpc request.
Other methods that call request_dump like getBootStrpPeer is not
include.
testRegistryClient test the rpc call with or not with "cn" parameter.

cli.conf: test each situation call the cli conf.

tunnel: add test for BaseTunnelManager, MultGatewayManager

tools is a util cotain method to make cert and ket files