Feature: Practice mode

[percyqaz]

key ideas

• warmup tools
• metrics for repetitive practice of fundamentals
• ability to repeat a section of a song over and over
• LN ultra grind tools and stuff (pattern generation ideas at play)

had a great convo with qqp about how lacking vsrgs are in practice tooling

[percyqaz]

More/related ideas on this:

All-purpose "Tracker" screen or "Dashboard" screen

• Manages score buckets, see #71
• Displays score buckets (buckets with updates most recently shown first)
• Displays goals (goals with progress most recently shown first)