Part of #2478 - [3] Tradingview indicator import functionality

**Is your feature request related to a problem? Please describe.**

I'm unable to import my own tradingview indicator. I want to create a sine wave indicator for the [Hz](http://open-explorer.io/#/assets/hertz) MPA which other Hz users can import to improve hertz sine wave visualization.

**Describe the solution you'd like**

Support client-side import of tradingview indicators (pine script?)

**Describe alternatives you've considered**

Customized BTS wallet to include the sine wave indicator. 👎

Get indicator included in bitshares-ui, but only activate on Hz pairs? 🤔

**Additional context**

Check out [startail's hertz chart site](https://crypto.fans/hertz/) shows a projected sine wave reference indicator which helps users indicate the current Hz phase.

The issue does not identify a file, test, or existing indicator entry point. Start by locating the client-side chart and indicator-handling code in the bitshares-ui repository, then determine how TradingView/Pine Script indicators could be imported and represented. Done would mean users can import an indicator such as the Hertz sine-wave reference and use it in the chart.

Written by the indexing model from the issue text.