Allow to reformat flow collections

[perlpunk]

There are a number of styles to consider:

# everything on one line, until line length exceeded
compact: [aaaaaaaaa, bbbbbbbb, [cccccccccc,
      dddddddddd, eeeeeee]]

# new line when collection is started
medium: [
    aaaaaaaaa, bbbbbbbb, [
      cccccccccc, dddddddddd, eeeeeee
    ]
  ]
medium2: [ aaaaaaaaa, bbbbbbbb,
    [ cccccccccc, dddddddddd, eeeeeee ] ]

# every event on its own line
verbose: [
    aaaaaaaaa,
    bbbbbbbb,
    [
      cccccccccc,
      dddddddddd,
      eeeeeee
    ]
  ]

There might also be styles with slight variations.
Also the number of spaces before/after []{}, should be configurable.