Expand example logging for multiple logging platforms

Following up on the discussion from issue #79, there is a need to extend the logging capabilities for keeping track of training figures (e.g. showing attention, forecast quantiles, etc.) for loggers beyond tensorboard (e.g. W&B). The self.logger.experiment.add_figure() lines that exist in models.base_model seem to be the route of the issue, as not every logger platform has an add_figure() method for its experiment (or Run in W&B's case) objects.

This is a to-do item for now. Can currently be circumvented (at least in the case of using W&B) by setting log_interval=-1 in the instantiation for TemporalFusionTransformer object.

Start by reading the discussion in issue #79 and inspect the self.logger.experiment.add_figure() calls in models.base_model. Compare the logger interfaces mentioned in the issue, including TensorBoard and W&B, and determine how figure logging should work across them. Done means training figures such as attention and forecast quantiles can be logged without relying on log_interval=-1.