Author: B Tasker <github@<Domain Hidden>>
Date: Tue Jul 04 10:27:19 2017 +0100
Commit Message: GPXIN-34 - Normalise elevation attribute name in trackpoints to "ele"
To avoid break b/c, "elevation" remains valid but should be considered deprecated and will be removed at some point.
In a GPX file with 2100 trackpoints, having both set makes the serialised JSON approximately 8K larger.