Update qsynth to 0.6.1
- Custom color (palette) theme editor introduced; color (palette) theme changes are now effective immediately, except on default.
Test Plan: Make sure that qsynth loads and test the color palette.
Reviewers: Triage Team, DataDrake
Reviewed By: Triage Team, DataDrake
Differential Revision: https://dev.getsol.us/D7882