Refactoring or CSS helper steps in common-utils

- Made steps somewhat more low-level/atomic. They now match better the
  basic CSS processing steps as explained in the specification.
- Made the steps more self-documenting: step names, elements and
  attributes are expressed as much as possible in terms of CSS concepts.
- It is now possible to deeply parse a document and obtain a
  fully-fledged intermediate representation of the document according to
  the CSS model, that is better suited for further processing by a
  renderer.
- Updated dotify-formatter accordingly.
Use Dotify through OSGi services instead of Spi Fly
dotify-calabash: translate generated numbers to braille