Preserve original comments

[angelolloqui]

Current version transforms Swift code to an AST and then back to Kotlin, but the initial comments get removed.

A possible solution would be to look for all comments (contained in the TopDeclaration) and look for the closest node in the Swift code and place it next to the first corresponding Kotlin token. This strategy could result in comments wrongly placed in some circumstances, but should work OK on most cases.

[prattcmp]

Id just like to add this could be super useful for iOS devs communicating code to Android devs.

[angelolloqui]

Merged with 73a4c52