Create a pipe for rendering the currency values

[AlexITC]

Create the explorerCurrency pipe that takes a number and renders it our currency symbol

Expected behavior

It should be possible to render amounts with this: {{item.value | explorerCurrency}}

Ideally, the currency symbol will be taken from a configuration file.

Actual behavior

We use the following approach to render the explorer amounts: {{item.value}} {{'label.coinName' | translate}}

This has several drawbacks like requiring to repeat the translation key on every language.

[AlexITC]

This is very similar to the work done on #42