Size: Refactor _fnBrowserDetect slightly to reduce size a small amount
Update exposed functions list
Dev - code regoranisation for new methods

- Variables and functions which are to be private in DataTables, but
  available across all files have a single leading underscore.

- Variables and functions which are to be private in a single file have
  two underscores (but no self executing function to restrict scope as
  that will just take extra space).

- Externally exposed functions and JSHint globals list updated