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!
RouteSegment: Add a new sidebar
IntervalView: Add a new intervals View
IntervalNavigator: Add new files
IntervalNavigator: Remove intervals from SubRide
IntervalNavigator: Add the interval
Make Intervals view optional till v3.2

.. we will develop over the next few months but it will
   not be ready for v3.11 so making it optional.
Gear Ratio SEGV Hack Fix

.. need to check if this hack fixes SEGV before raising
   with Joern.
Updated Merge Tool Part 2a of 2a/b

.. page flow and join sorted

.. committing before resolving the merging code
   - analyse() to identify offsets
   - combine() to merge into a working copy
   - ux for sliding offsets on a fullplot

.. next commit will complete this update to the
   merge tool

NOTE: MERGE IS NOT CURRENTLY WORKING SO PLEASE
      DO NOT USE IT !!!!
merge upstream into master