APR breakdown tooltip

[Yanivshechter1]

As a user, I would like to better understand the APR components.

High level

Adding APR breakdown tooltip to earn table and token page

Tooltip

1. Mockup - https://www.figma.com/file/fwADI9wqDrRAdlMX8EddCw/Bancor-v3?node-id=15566%3A231154
2. Behavior - Show the tooltip when hovering over the APR number
3. Location - Earn table (when hovering over the individual row APR) & Token page (when hovering over the APR on the top right)

Tooltip data

1. Compounding Fees -> show the "fees APR"
2. Compounding Rewards -> IF >0, show the "compounding rewards APR"
3. BNT Rewards -> IF >0, show the "standard rewards APR"