Support for multi-output label (multitask learning)

[bagustris]

The current behavior of Nkululeko only supports a single target (e.g., target = emotion). Given that scikit-learn supports multiouput labels, it is possible to make Nkululeko also support multitask learning.

Imagine that we can do,

target = ['emotion', 'age', 'gender']

in the INI file.

For the first start, one could change the format of the target from target = emotion to target = ['emotion'] and do the rest later.

[felixbur]

interesting-
need to look into this
I don't think though that target should be a list until it's implemented