API: Update to extension API for camelCase support and tidy up

- This is a fairly far reaching commit in that the DataTables.ext object
  is updated to primarily use camelCase, just like the rest of the 1.10
  API. The old notation is still available for compatiblity, but
  deprecated.

- While working in this area, I've made a number of updates:

  - .model.ext has been removed - that was redundant and not useful.
    DataTables.ext is where the plug-ins for DataTables will live and
    will be correctly publically documented as such.

  - Type based actions (detection, sorting and filter) now live in a
    `type` namespace to make it clear that they are type based.

  - Internal references to .ext updated to use the new parameters. We
    could use the old ones since they are fully backwards compatible,
    but I'd rather set the standard by using the modern ones.

  - JSDoc comments for .ext updated

  - Extension examples updated