Crop / Split Improvments: disabled crop button, split via range, higher contrast in elevation profile (dark theme)

[SVNKoch]

• Bug: open the crop menu, then select a range in the elevation profile => Crop button is disabled; once you touch the crop slider, then selecting a range in the elevation profile works.
• Additionally to cropping (as in deleting preceding and remaining segment), there should be the option to split the trace in 3 (/ 2 when at start / at end). With the option to store them as files / tracks / segments.
• The contrast of the range selection in the elevation profile in dark theme a) looks inverted (applies to light theme too) b) has too too weak contrast Currently: Mockup:

[SVNKoch]

maybe even add a vertical line / arrows or some other indicator in the elevation profile Because sometimes the low elevation makes it impossible to see otherwise: (selection is from middle yellow to red line dropoff)