Create workout - start elevation graph at 0

[joshwouden]

Enhancement Details

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Description
The graph view while creating a map based workout displays the changes in speed, incline, and elevation throughout the route. The elevation graph displays the actual elevation rather than the elevation change (so when drawing a graph in logan, the line begins at ~5k ft and changes from there). This is counter-intuitive and makes the actual elevation changes difficult to see (since the graph is zoomed out so far, the changes look slight). in other parts of the site, we have changed graphs like this to display the relative elevation change.

We might consider updating this page to match the rest of the site and display the elevation changes of a workout in a more relevant, useful way.

Screen-cap

Reproduction Steps
Create a workout
Click Graph
Note that the elevation line (under Overview) starts high on the graph and changes from that point rather than starting at the bottom of the graph

Notes
See #5842
@joeyhdez10