NetworkTables freeze bugs across C++/Java/Python

[virtuald]

Some of you may remember this bug from last year that affected C++ teams. If you look at this year's NetworkTables code... pretty sure it's still there, somehow the patch slipped through.

I really like the idea of NetworkTables, and SmartDashboard/SFX are super useful -- so I spent a week examining the python NetworkTables implementation. I've identified at least two other places (though, I'm sure there's more) where deadlock/increased latency is possible -- and these places are the same across all three languages. I've written some details on this github issue.

pynetworktables has fixes for these bugs, and should be pretty stable as of 2015.1.0.

I am not planning on fixing the other platforms, as I've already spent enough of my life fixing networktables bugs But hopefully this information can help someone else fix it.