Indent nested method-call argument lists (#591)

[austek]

Summary

Fixes #591. Adds extra indentation for nested method-call argument lists whose contents start on a line after the opening paren.

For a multiline statement like

println(m1().
        append("a").
        append("b").
        append(m2(
        "x",
        m1())))

the existing formatter applies a single multiline indent to every continuation line, so "x" and m1() (inside m2(...)) end up at the same column as .append(...) from the outer chain. The new handleNestedParenWraps pass in GroovyIndentation walks the tokens and, for each paren pair that

• opens with content on the next line (a wrap-open), and
• is itself contained within another paren

adds another indentationMultiline step to the lines it spans. The outermost wrap is left to the existing multiline-statement rule, so the single-level fixtures (MultilineStatements1/3, MultilineMethodParams*, etc.) are unchanged.

[eric-milles]

I'm not sure how far the pattern of a separate method for each kind of wrapping is going to be doable. But thank you for your contribution.