Add new loss functions on training

[sagnik1511]

1. Add 3 loss functions for both regression and classification problem types.
2. Add them similarly to how the model scores are stored. See here
3. Add proper comments.
4. If new functions are needed for the loss functions, store them on tab_automl.utils.training .
5. Update the requirements if new libraries are being used.

Follow contributing guidelines on README.md

[das-ankur]

I want to work on this issue under JWOC

[sagnik1511]

Please make sure that you add atleast 3 loss functions. Good Luck!

[das-ankur]

Hello, I need help. Can you please tell me, do I need to store the py files in utils?

[sagnik1511]

1. First store the functions inside utils.training
2. Use those functions on the main training file.
3. If you want another function to iterate through those loss functions, create another function under the class Trainer.

[sagnik1511]

Hey @das-ankur, any update on the task?

[sagnik1511]

As 5 days have been completed, @das-ankur please update the task details so that I can merge that, no response will be recorded as an incomplete task.

[das-ankur]

I'm really sorry for the late reply, I have had a fever for the last two days. I will do PR by Tuesday.

[sagnik1511]

Unassigned @das-ankur