[21] Kelp GUI should support the pendulum trading template

[nikhilsaraf]

Desired Behavior

I want to run the pendulum trading template using the Kelp GUI

Impact

The desired behavior will allow me to use more trading templates with the Kelp GUI

Feature Suggestion

We can achieve the desired behavior by:

1. Update backend API to accept new fields when saving/updating a bot config
2. New frontend UI elements to send through the API

Specification

If possible, this should be done in a generalized enough manner to where it becomes easy to add a third trading template.
There are two ways to generalize this:

1. backend needs to be generalized to where it recognized a fixed set of hard-coded trading strategy template names. We don't need to fetch this from the backend for this issue but the backend should validate against this array/map. backend then needs to substitute the correct parameter in the cli command to run kelp (in particular the arg that goes to the -s flag), and also name the log files appropriately, and pull from the correct sample_template file. This is pretty much it.
2. UI needs to be generalized to where it fetches the UI fields from the backend and renders the associated components on the frontend. This would allow us the flexibility of auto-rendering UI components for future trading templates that we incorporate.

(1) is in scope for this issue
(2) is out of scope for this issue. For the frontend we should just hardcode the fields and the trading template name as "pendulum".

Note that we assume throughout the codebase on the frontend and backend that there is only one trading template called the buysell template so this may need to be checked thoroughly since pendulum is the second template we are adding to the GUI

[igorsinkovec]

Getting ready to take this issue.