dart format should preserve vertically-aligned formatting

[chipweinberger]

Dart format should not make carefully considered indentation harder to read.

In practice I think comments that are vertically aligned should be ignored, or there should be some opt-out.

Potentially, vertically aligned comments should be the default.

before formatting:

enum BmAdapterStateEnum {
  unknown,      // 0
  unavailable,  // 1
  unauthorized, // 2
  turningOn,    // 3
  on,           // 4
  turningOff,   // 5
  off,          // 6
}

after formatting:

enum BmAdapterStateEnum {
  unknown, // 0
  unavailable, // 1
  unauthorized, // 2
  turningOn, // 3
  on, // 4
  turningOff, // 5
  off, // 6
}

[srawlins]

Duplicate of #48