Updated Merge Tool Part 1 of 2

.. data can be sourced from file, download or list

.. next to update the mode (join or merge) and the
   merge strategy and parameters.

.. will also need to update the download dialog to
   allow you to specify which downloaded rides to
   process -- at present the merge tool assumes that
   the download dialog will only return 1 result

.. pleased with the way the download dialog is embedded
   within the wizard, will use that for other things!