ANJ: converter refresh (encapsulate both Uniswap and bonding curve)

[sohkai]

Idea

User story

As a user, I would like to get the best price when I want to convert ANT into ANJ, or convert from ANJ to ANT.

Requirements

• The user must be able to see their wallet and registry activated balances of ANJ
• The user must be able to select whether they want to convert into ANJ or back from ANJ ("buy" vs. "sell")
• On token -> ANJ:
  • The user must be able to select multiple token sources when converting into ANJ via Uniswap
    • If ANT is picked, the converter should take into consideration both the Uniswap rate and the bonding curve rate, and suggest one over the other to the user if there is a big differential (if not great, default to Uniswap)
• On ANJ -> token:
  • We should only provide ANT as a token; any other tokens should be done via Uniswap directly
  • Similarly to the other direction, the converter should take into consideration both sources

Notes:

• The Uniswap wrapper can immediately activate any received ANJ, whereas the bonding curve cannot (so it will always directly going to the user's wallet)