Diagnostics sans ganglia

Logs the diagnostics data directly in to CloudWatch and gets rid of the odd ball nginx log tailer we were using.

It stores a set of counters in a singleton, then batch loads them in to CloudWatch every 60 seconds, before resetting them.

You can test it like so,

http://localhost:9000/px.gif?type=js&message=foo

BTW, I've not done the corresponding platform tasks to remove nginx etc.