Explore different active learning strategies

[MaxHalford]

• We now have an active module for online active learning.
• Right now it contains a single strategy based on entropy.
• The goal is now to explore different strategies we can find in the literature, and implement what works best.

Links

• https://cilvr.cs.nyu.edu/diglib/lsml/lecture12_active.pdf
• https://icml.cc/Conferences/2009/papers/392.pdf
• https://raw.githubusercontent.com/wiki/VowpalWabbit/vowpal_wabbit/cs_active.pdf