New: columns and cell index() API methods

- The row()/rows() methods have index methods, so it makes sense that
  the column(s) and cell(s) methods also have index methods to get the
  raw information out of the table. Rather than shying away from the
  indexes in 1.10, as has been done with the pervious versions of
  DataTables, 1.10 will embrase them as first class citizens.

- New methods:
  - columns().index()
  - column().index()
  - cells().index()
  - cell().index()
Dev fix: Fix case where trying to select row index 0

- row(0) was failing due to a logic error in the selector, which was
  ignoring the 0, or rather, treating it like an empty selector.
Dev fix: Fix flatten, which was returning an array rather than an API
instance
Dev fix: Fix new filtering API which was incorrectly assinging undefined
values to the filtering operators
Dev fix: rows.add() API was trying to get the row index from the wrong
parameter.

- Simple fix, just had the array index in the wrong location.
Dev fix: Fix name conflict and adding of TR elements

- There were two functions called _fnGetRowData, which were conflicting

- The $().map doesn't execute with the scope of the element, need to
  pass the element through to the get data function correctly.
Update: Deprecate old API. update `api()` method.

- With the new API that is being introduced in v1.10, the old API
  (fnUpdate, fnAddData etc) is being deprecated and retired. It is now a
  shim layer calling through the new API, rather than duplicating the
  logic of the calls, but is still provided for backwards compatiblity.

- It is _strongly_ recommended that you start to use the new API from
  this point in - very certainly for new projects.

- The api() method, is not deprecated, it is new in 1.10 and provides a
  way to get access to a DataTables API instance from the jQuery host
  object, if the table is initlaised with `dataTable()` (rather than
  `DataTable()` which does give you the API instance. It has a single
  option which is used by the old API's shim layer to allow it to use
  the iApiIndex option to get the context to be used.