Adjacent orphan cells/rows should be normalized inside a single row/table

[Soreine]

The PR #17 added a schema rule that prevent orphan cells or rows to exist, and wrap them in tables.
An enhancement would be to wrap adjacent cells or rows together.

The current behavior:

- cell
- cell

gives

- table
  - row
    - cell
- table
  - row
    - cell

Improved behavior

- cell
- cell

should give

- table
  - row
    - cell
    - cell