Changed scope names to match the style recommended by TextMate[1].

- All names now correspond to a matching internal, predefined scope if they can fit (e.g. links are under markup.underline.link, headings are under markup.headings).
- Every scope defined in the syntax file now has its own "meta." scope as well. This will allow themes to style Confluence wiki files without messing with the generics, if they so choose.

  [1]: https://manual.macromates.com/en/language_grammars#naming_conventions