Fix - examples: Same id twice on the page breaking things
Fix: Initialisating multiple DataTables with a single call was broken

- Because of the manipulation of the initalisation object initialisation
  of multiple tables with a single jQuery call (i.e.
  `$('.dataTable').dataTable();`) was broken since the second table
  would see the modified init object. Need to take a coopy of the object
  before entering that state.

- This could probably do with a bit of a clean up sometime...
API - invalidate() methods - add an "auto" option that can be passed
rather than jsut an empty string as auto
Docs: row() and rows() API documentation
Dev fix: The API chaining was a little broken if the inner function
returned undefined, null etc.

- The base issue was in the instanceof check which has a priority error,
  it was:
    ! obj instanceof _Api
  which is the same as:
   (! obj) instanceof _Api
  which is rubbish.

  We want:
    ! (obj instanceof _Api)
  but there is of course a wrapper function, so that needs ot be taken
  into account as well. The new logic does just that.
Dev fix - incorrect fix for the API extend method before. Was looking
its own reference
Api: Column selector - jQuery selector as a string, an name selector
with :name postfix.

- Previously you could use a jQuery selector for columns by using the
  :jq postfix, and names were matched otherwise. This is reversed now
  for consistency with the rows and cells selectors which treat strings
  as jQuery selectors without the :jq postfix.
API: Column selector - add support for visible indexes counting from the right

- The ability to use negative numbers as a column selector for the
  column data index was added recently, but that didn't include the
  ability to work with negative numbers with the :visible pesudo
  selector. This commit adds that ability so you can do:
  `table.column("-1:visible")` to always get the right most visible
  column