Fix the value shown on a balance update transaction

[ahatzz11]

I noticed today that when editing a balance update transaction the amount shown didn't respect the currency steps. After some playing around and looking at the normal transaction (which worked correctly), I believe this fix is appropriate. I tested this locally and it works great (I tested USD and JPY for different precision values from currencies.yml)

This is where I saw the value field for the money_field of a normal transaction:

maybe/app/views/account/transactions/show.html.erb

Line 57 in 56ab092

value: entry.amount.abs %>

Before/After:

Fixes #1447

[zachgoll]

@ahatzz11 we probably should avoid calling abs on this for the case where a user has entered a negative balance on the account (rare, but possible and valid).

Just pushed through a fix that addresses this at the form builder level using the _money_field partial:

31ecd3c