Code Engine: Support for process.argv

[marusshi]

Is your feature request related to a problem? Please describe.
For the IoT benchmarks, we want to be able to easily vary the rate at which the spout node emits the data.

Currently, we can edit the setInterval rate in the source code, but this requires multiple "versions" of the same code with different setInterval rates.

Describe the solution you'd like
Something akin to process.argv for Code Engine that would allow the code to be more reusable, e.g. a CodeEngine.runCode equivalent of:

> node SenMLSpout.js 3000 : emit data at a rate of 3s

Describe alternatives you've considered
Just alter source code