utilise configparser's ExtendedInterpolation functionality

[laurencejackson]

using the extended interpolation fucntionality will mean we can pass the data path from the config file straight into the entry point .e.g.

instead of:

[entry_points]
main = python3 train.py  /DATA/BarrettsPathLabelled_2.csv
tune = python3 tune.py  /DATA/BarrettsPathLabelled_2.csv

we can use:

[entry_points]
main = python3 train.py ${data:DATA_PATH}
tune = python3 tune.py ${data:DATA_PATH}

[data]
DATA_PATH = /DATA/BarrettsPathLabelled_2.csv

example implementation https://stackoverflow.com/questions/42839889/extended-interpolation-not-working-in-configparser

[laurencejackson]

Changes to the way projects are run since #92 means that this is no longer applicable