[ETHEREUM-CONTRACTS] Completness of the upgrade/downgrade flows of Super Tokens

[hellwolf]

(... per community input ...)

Notes

Extend SuperToken upgrade/downgrade with more overloaded versions of them.

• upgrade(amount)
• upgradeTo(to, amount) # *
• upgradeTo(to, amount, userData)
• upgradeFrom(from, to, amount) # *
• upgradeFrom(from, to, amount, userData) # *
• downgrade(amount)
• downgradeTo(to, amount)
• downgradeTo(to, amount, userData) #*
• downgradeFrom(from, to, amount) # *
• downgradeFrom(from, to, amount, userData) # *
• expose the underlyingAmount <-> supertoken amount arithematic to the user for easier integration. Using the example from TOREX BLM for reference.
  • e.g.: toUnderlyingAmount/fromUnderlyingAmount/toSuperTokenAmount ?

We do not add these, in favor of the macro versions:

• downgradeAllTo(to)
• downgradeAllFrom(from, to)