* Allow 0% slippage, show a warning for 0 < slippage <= 1, disable “Review Swap” button for negative slippage
* Update a translation key, use both new and old key until it’s translated everywhere
* Keep an old key for `en`: swapSlippageTooLow
* Fix an ESLint issue
* Only use swapSlippageNegative, remove swapSlippageTooLow
* Increase default slippage from 2% to 3%, show Advanced Options by default
* Disable opening / closing of Advanced Options on the Swap page
* Pre-select previously used slippage value when going back to the Swap page
* Fix lint issues
* Use a callback for setting up an initial customValue
This fixes a PropType error when using non-custom slippage, and it
fixes a type inconsistency when custom slippage is used.
Previously, `slippage` was being converted explicitly to a `Number` as
it was passed into `BuildQuote`, but not as it was passed into
`AwaitingSwap`. Also the PropType was set as `string`, despite the fact
that it's a number in most cases, and is used for math.
The PropType has been changed to `number`, and the selective casting to
`Number` has been removed. Instead, the `maxSlippage` value is cast to
a `Number` as it's being selected, so that the type is always
consistent.