libdpx: move back to libtask for shared library support
pyduplex: Initial commit.
bindings/pyduplex: initial implementation of pydpx
bindings/pyduplex: more fixes, but segfaults

Needs investigating into how ctypes returns a pointer that we
can use later (from dpx_peer_new(), because bind fails).
bindings/pyduplex: fix basic sending/receiving of frames
bindings/go-duplex: add support for switching codecs
bindings/pyduplex: finish all tests for pydpx (passing!)
Merge branch 'dev_libtask_again'

Closes #2