Mechanism for passing date and parameters for potential runtime usage

[leclairm]

The issue

At runtime, tasks could potentially need access to:

• their own date and parameters
• date, parameters, port and path of input data

Potential solutions

Environment variables

Could work for the task itself, probably cumbersome for input data

Written to file

This file would be dumped in the working directory where the task could read it.
Similarly to #49, the format of choice is important. yaml is well suited for python, not at all for shell scripts. Maybe a basic text file in that case or a file to source, removing the need for parsing on the user side.