pycriu: add python package

pycriu is a python package, that, for now, consists
of rpc module and images package. rpc module contains
data structures for interacting with CRIU RPC.
images package contains methods for loading\dumping
criu images.

See a big comment below in pycriu/images/images.py file.

Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>