Dev: Reduce code footprint for the Ajax get function
Dev: Documentation update to indicate more clearly that dataSrc can be
used as a transform function
New: HTML5 data attribute support. data-* attributes can now be used to
source orthogonal data for filtering, sorting and type detection data.

- In HTML5 the data-* attributes can be used to add semantic data to an
  HTML page, which a user will not see, but the scripts on the page can
  interact with. DataTables now has the ability to use these attributes
  (actually any attribute can be used) as a data source. Previously DOM
  sourced tables always used just the content of the cells for all data
  interaction, but this can provide advanced controls in just the same
  way that Javascript / Ajax sourced data can do orthogonal data in
  DataTables.

- A typical use case is to provide numeric sorting information for
  complex formatted dates that the browser doesn't understand with
  Date.prase().
New: Automatic detection of HTML5 data-* attributes for orthogonal data

- Building on the new ability of DataTables to work with element
  attributes as data sources for sorting and filtering, this commit adds
  auto-detection of the attributes 'data-sort' and 'data-filter' in DOM
  sourced tables.

- The first row in the table is used for this auto-detection and the
  built mData object assigned only when it is found to be the default
  for the column (i.e. the column index). So any custom value is
  retained and thus if you want to use a custom value you need to build
  the attribute querying object manually (I think the majority of uses
  will not need this!).