Add an annotate stage and more options

[TimothyGu]

This module is getting messy. It would help if we have a separate annotation stage for choosing the layout of a block.

For example, for the following source we can generate all sorts of blocks. Depending on user-supplied options and possibility we should annotate the blocks with properties that help doing such things.

div
  p
    | hey #[strong text]
div
  p
    | two line
    | text

Base output (all options at false):

div
  p hey #[strong text]
div
  p
    | two line
    | text

1. aggressive inlining (unrelated to performance)

   div
     p hey #[strong text]
   div
     p two line
       | text

2. use block expansion for a block

   div: p: hey #[strong text]
   div: p
     | two line
     | text

3. use dot

   div
     p.
       hey #[strong text]
   div
     p.
       two line
       text

4. And any combination thereof:

   (dot and expansion)

   div: p: | hey #[strong text]
   div: p.
     two line
     text

   (inlining and expansion)

   div: p hey #[strong text]
   div: p two line
     | text

A propose to have the following defaults:

• block expansion: auto: only when there is only one node and one level of node and if the lowest level is text, it has only one line. so

  div
    p
      strong
        | hey
  div
    p
      strong
        | multi
        | strong
  div
    div
      p multi
      p line
  div
    p
      img

  turns into

  div
    p: strong hey
  div
    p
      strong
        | multi
        | strong
  div
    div
      p multi
      p line
  div
    p: img

• aggressive inlining: false as it looks ugly

• dot: auto: use the current heuristics that I believe it works well enough: use dot syntax when there's nothing besides buffered code and text, and (number of whole lines of code)/(total lines) < 0.35