Convergence stats

[mortonjt]

This pull request creates summary statistics to help evaluate loss curves in the qiime2 interface.

In short, we have enabled the following

• summarize-single to view a single model's loss curves
• summarize-paired to compare two model's loss curves (also allows for null model testing)
• GPU-acceleration in the qiime2 interface
• Better defaults for parameters

Below are some images showing what the new summaries look like

The tests are expected to fail for now, since the APIs have slightly changed, we'll need to fix those before merging.

Otherwise, this is ready to start testing. CC @mwang87

[mortonjt]

Merging. We will need another separate PR to touch up on the docs.