Transfer and Approve event naming inconsistencies

[monitz87]

I found an inconsistency in the naming of the Transfer and Approval event parameters between PolyToken and PolyTokenFaucet. In PolyTokenFaucet all parameters are prefaced by an underscore (i.e. _from, _to, _value), while in PolyToken they are not. This causes inconsistent behavior when switching between mainnet and kovan in the dApp.

I suggest renaming the PolyToken event parameters to include underscores as defined by ERC20

[maxsam4]

Can't change PolyToken as it's live on mainnet. I'll refactor PolyTokenFaucet.

[monitz87]

I understand, wasn't really thinking when I suggested it haha

[maxsam4]

ERC20 standard defines the event parameter names with underscores.

Refactoring of PolyTokenFaucet depends on what OpenZeppelin decides to do
OpenZeppelin/openzeppelin-contracts#1175

[maxsam4]

Fixed in #480