Creating error/Warning message ui box

[aarexer]

Sometimes when we have error or warning and it will be really great if we show warning or error messagebox in that case. Unfortunately in javafx standard library we don't have ui messageboxes.

As i see we have two variants:

1. Write our own ui interface for it.
2. Find and use external library - it's common problem and i am sure that somebody wrote it.

I think we should start from second variant.