Refactor TypesDB
Add unit & bench tests for Packets
Don't use binary.Read for packet header

Switching to binary.BigEndian.Uint16 almost doubles the speed
of packet parsing.
Merge branch 'dgnorton-master'

https://github.com/kimor79/gollectd/pull/1
TypesDB usage has changed
remove unneeded comment
Slightly more consistent error messages