Use lazy for WorkingBeatmap component loading
Optimise leaderboard display
Various improvements to make DifficultyCalculator support mods
Fixes https://github.com/ppy/osu/issues/476.
Adds async loading support and cleans up the code quite a bit in the process.
- Also unbind event handlers - Remove unused field
Add top scores section into beatmap overlay display
Fix hard crash when clicking play button with no map selected
Ensure only one information overlay is open at once