* add option "host_netns" in configuration to move the host veth
  interface in a specific netns
* add options "route_source_interface_ipv4/ipv6" to change source IP
  used in routes configured by the IPAM plugin
* add option "sysctl", taking as input the same format of configuration
  than the "tuning" plugin to configure sysctl parameters in the
  container netns

* result needs to be converted to the right CNI version before passing
  it to another plugin

* when using route_source_interface, we expect to have a single IP
  configured on the interface, however in IPv6, there is always a link
  local address configured in addition to the one provided by the IPAM
  plugin
* getIntfIP function was returning an error as we were seeing 2
  addresses instead of 1, now we filter this link-local address to fix
  it

* default route in IPv4 and IPv6 is equivalent to a Dst = nil in a route
  filter

* we must check that all the new config parameters have been correctly
  set on the host/container netns

* the sysctl feature might be unnecessary as we could configure sysctl
  parameters on the host itself, or via the mesos isolator
* we'll repropose that feature again if this is needed