Feature Request: Allow "sort by elevation gain" when browsing mountaineering activities (with hiking activities this is already possible)

When browsing though mountaineering activities it's currently not possible to select a columns to display elevation gain values and sort by such values.

Filter-values-dialog only gives a few options. It would be nice to have the whole set of recorded values for selection.

Screenshot of hiking with Elev. Gain column 

Screenshot of hiking filter and its elevation gain column

Screenshot of mountaineering filter

Screenshot of mountaineering selection

Screenshot of filter dialog

Screenshot of available values for column/sorting

Thx in advance ;) 

Cheers, Andy