rate-tr-j.R changed to obtain InData kbit/s

Modified the script so that it would graph OutInterests and InData which tend
to be the most important for graphs.
Error in PayloadSize calculation

Due to a forced cast of int, the PayloadSize was coming out as 0, which was
not what we wanted to achieve. In this commit, this error has been resolved.

There have also been some changes to the logging, to make it a little easier
to debug issues found.