Various bug fixes including bar numbers for Dark Mode

- Users can now export the multitrack version of each song (native pitch and tempo only) at no extra cost. This was previously an in-app purchase.
- New hi-hat count-in option. Available via Global Settings and also individual songs.
- Minor re-working of the home page song layout.
- Permanent fix for users who have 'Display Zoom' enabled on their device.
- Various bug fixes.

Bug fixes and correction to Winter Wonderland