More thorough support for newlines across the grammar

[ForNeVeR]

For context, see #236.

Should fix #182.

Closes #236 (as superseded).

TODO:

• [ ] Make the existing tests green
• [ ] More tests for the initial case

[ForNeVeR]

Folding / expand selection difference (folding.ps1). Main:

PR:

Trailing spaces are no longer considered a part of the block. This is incorrect and we'll need to fix it somehow before merge.