Merge pull request #1186 from amtriathlon/master

Fixed copy and paste error
QVector::removeAt(int) is new

.. so use ::remove() instead for QT4 compatibility.
Remove Zones from RideItem

.. they are in Athlete::zones() et al now

.. this refactor was missed in the 3.0 mainwindow
   refactoring and is part of the prep to use RideItem
   as an in memory cache instead of the old metricDB
Fixup 3D plot for RideItem zones

.. missed in last commit.
Tidy up RideItem.h

.. the cache code can start now !
Added RideMetric::index()

.. each metric now has an index (identifier) that can is numeric
   starting at 0 and going up.

.. it can be used to offset into an array when we add a cache for
   storing precomputed metrics.