#254 Code Formatter: line-break styles for long uses clauses

[Thomas Mueller]

Let the formatter break long uses clauses at the maximum line length, with a choice of style:

• one unit per line
• wrap at the right margin
• comma at the end of a line or at the start of the next one

The maximum line length could be taken from the IDE's Right Margin setting instead of a separate formatter setting.

Related: #90 asks for one unit per line in the Uses Clause Manager.