Changes to icons in profile panel

- Replace dustbin icon.
- Replace NDL/TTS tool tip with "Show NDL / TTS"
- Create tool tip for scale icon: "Rescale depth axis"

Signed-off-by: Willem Ferguson <willemferguson@zoology.up.ac.za>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>