Switch to loxigen-built openflow.lua wireshark plugin

The older wireshark dissectors were not well-maintained
and were a pain to build. They also added tons of extra junk
into our VM images! The ones built into the current
wireshark are deficient for 1.3. The solution for the
future is almost certainly to go with the lua-based plugin,
since it is architecture-independent and should be much
easier to maintain and upgrade.
Don't install lua plugin for wireshark 1.12+

Apparently there is a conflict where the lua plugin
conflicts with the built-in dissector for openflow
that is included with 1.12 and up. For now, we will
just not install the plugin. This should fix the
14.10 VM build.

Additionally, I have added a handy function,
version_ge, which compares version numbers in
canonical x.y.z format. Thanks to stackoverflow for
pointing out the incredibly useful sort -V option!
Install coloring rules regardless of plugin. Also don't clobber.
Merge pull request #384 from mininet/devel/loxigen

Switch to loxigen-built openflow.lua wireshark plugin