Add support for Realapp objects taking different algorithm transformers per explanation type

[zyteka]

Realapp objects should support taking different algorithm transformers by explanation type - after all, this was the original purpose of having algorithm transformers.

Some things we need to think about:

1. Users need to somehow specify the order that transformers should be run; so they can't simply pass in additional transformers
2. User may want to remove some transformers for a specific explanation type
3. We need to store each set of transformer for future use

The easiest way to meet these requirements may just be to have users pass the full transformer list whenever they want something different.