Gen: NewTransform final touches

[jonasmalacofilho]

Continuing from #5, we still need to:

(Syntax/transform:)

• [x] fix #1
• move empty element checks (i.e. section names) from the parser to the transform
• support for manually setting id (and better support for automatic ids)
• [ ] more tests
• [ ] documentation for tree and implementation
• [x] removing remaining pieces of the old Transform

[jonasmalacofilho]

I need to merge this now, so I'll create issues for the remaining tasks.