Add get_interfaces to the API

get_ips accepts an interface name as a parameter but there was no
way to get the interfaces names from the container. This patch
introduces a new get_interfaces call to the API so that users
can obtain the name of the interfaces.

Support for python bindings also introduced as a part of this version.

Signed-off-by: S.Çağlar Onur <caglar@10ur.org>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>
Remove trailing whitespaces

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>