Implement rounding options for "Pay-By-Mail" payment type.

[wp07e]

#1014

Adds a combo box with rounding options to the nearest integers 1, 5, 10 or 20.

Tested on 1.0.7 seems to be working fine.

All other relevant totals (i.e. Amount of XMR to sell, Min amount of XMR) are also updated as well.

There is one slight issue where the new combo box seems to re-render out-of-order so I will prob. submit another commit to resolve that but its not a functional issue.

[woodser]

Issues observed:

• The rounding pull down needs a label, which uses in-built translations (can include default english to start):

• The pulldown should be disabled after the next button is clicked:

• Editing the offer does not update the rounded amount.

[wp07e]

Ready for review.

I considered various use cases and went through multiple scenarios including:

1. Creating multiple different offers with same / different payment account.
2. Checking Edit screen.
3. Canceling offer.
4. Completing trades on testnet.

[woodser]

Looks like the in-built tests need updated. You should observe the errors locally by running make.

[woodser]

Unless you're in some weird state, you should be able to simply git reset --soft <commit hash before first commit for this pr> then git push --force to squash all commits to one.

[wp07e]

Thanks

[woodser]

We can't change the numbering of existing persistent types, so this should be appended to the end and the other fields unchanged.

[wp07e]

Moved it to the end and resolved issues.

[woodser]

The pull down should only appear when applicable for the offer type:

Getting this error when making offer for BCH (probably all other non fiat types):

java.lang.NullPointerException: Cannot invoke "java.lang.Integer.intValue()" because "roundTo" is null
	at haveno.core.offer.CreateOfferService.createAndGetOffer(CreateOfferService.java:223)
	at haveno.desktop.main.offer.MutableOfferDataModel.createAndGetOffer(MutableOfferDataModel.java:286)
	at haveno.desktop.main.offer.MutableOfferViewModel.createAndGetOffer(MutableOfferViewModel.java:1139)
	at haveno.desktop.main.offer.MutableOfferView.onPlaceOffer(MutableOfferView.java:354)
	at haveno.desktop.main.offer.MutableOfferView.lambda$addFundingGroup$42(MutableOfferView.java:1213)
	at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)

[wp07e]

@woodser I addressed both of the issues you mentioned and I re-tested with normal and non-traditional (i.e. BCH) and everything seems to be working. If possible, please double-check thank you.

[wp07e]

@woodser Also, I think I want to try a ticket for the backend and was looking for a straight-forward, fairly easy one to start with. Do you think #1115 is a good candidate? If not, which one would you recommend to start with? No guarantees I will work on anything but just in case I decide to do it :)