Refactor: Store replays as a sequence of keyboard inputs

[percyqaz]

this one is more involved

Setup

Currently scores are stored as rows of information corresponding to each row in the chart The information stores the deltas of your hits/flags about needing to hit notes

Drawbacks are

• Cannot faithfully represent other engines like osu! with different LN mechanics or Etterna where cbrushing is basically the entire score system
• Code is somewhat difficult to explain/get familiar with
• Scores easily invalidated by bugs found and tweaks made to game mechanics
• Scores easily invalidated by glitches with mods and other issues

Solution

SCORE FORMAT 1: Stores a score as sequence of snapshots of your keyboard hits This is:

• How osu, quaver, soundsphere do it
• Easy to compress to potentially smaller than current score format
• More powerful, allowing the existing data to be calculated quite trivially from it
• Theoretically interoperable with osu, quaver and soundsphere scores/replays (we'll see)

SCORE FORMAT 2: The existing format

• This format becomes internal (format 1 is what is saved in the database) and used to provide information for the score screen - You calculate the data in a pass or live while playing as before, and it contains judgement counts/standard deviations/all that stuff

New drawbacks (old ones are gone)

• Need to know the note data for the chart in order to know anything about the score
• Need to know the modded note data for the chart in order to know anything about modded scores (These both impact server-side calculations of any kind)