flow_table:Fix non-strict delete flow_mods

Previously, all flow_mods were treated as OFPFC_DELETE_STRICT. We now
handle wildcards for OFPFC_DELETE.
pxpcap: Allow capturing to bytearray

Capturing used to always be to str/bytes, but can now be set to bytearray.
pxpcap: Set arbitrary properties via constructor

This is experimental.  The idea is that a user can set arbitrary
metadata on the pcap object before capture begins without having
to explictily call start().
pcap_switch: Start capturing later

We now set up all interfaces and do some other initialization
before starting capture.  This may avoid races.
messenger: Tweak test client code

This code was sort of confusing to read.  Better now.
pxpcap: Allow injecting from bytearrays

Previously we could only inject bytes objects.  We can now handle
bytearrays (and maybe even other buffer types, sort of).
packet: Don't try to pack unparsed packets

If a packet failed to parse, but has raw data, we now just use
the raw data rather than try to re-pack data that wasn't parsed
correctly to begin with.
libopenflow: Improve type guessing for stats_reply

ofp_stats_reply can guess its body type by actually looking at
the body.  Previously, this gave a non-obvious exception when
this fails because the body was an empty list-like object.
pcap_switch: Do pxpcap check inside launch

This way you can still import the module even without pxpcap (e.g.,
for the module load test), and it fails if you don't have pxpcap
when you actually try to run the component (which was the
intention anyway).
Merge remote-tracking branch 'upstream/carp' into carp