[Velocity]

I updated the urls to the v2 version. Also the file browser might show 5k & 7k files, but they aren't playable currently and I can't remember what happens if you try to load them.

Changes:

File Browser:
- Enabled by default.
- Add button on the song selection screen.
- Rewrite File Browser Loading:
- Now breaks up the initial file loading into smaller chunks, to avoid freezing.
- Loading and Initial Parsing can be canceled at any time.
- Song List now displays the chart source type, and the available key types.
- Song List maintains and more easily displays the currently selected song.

- Added Quaver [.qua] file support.
- Added SSC [.ssc] file support.
- Fixed BPM reliability in SM, and should fix sync on rare edge cases.
- Fixed Negative BPM / Warps, and should no longer generate impossible charts.