Add customizable shortcuts settings

[Ichunjo]

Draft until I implement the existing hardcoded shortcuts.
Feel free to give feedback if better approach or fixes.

[Ichunjo]

Should be ready to review.

Some key points:

• Do you want me to make separate PRs for the random bugs I fixed (884e0ba, 8477040, 7af0410 & 29a5776, 6c8ec90
• Plugins are lazily loaded but we need to make a partial load to get the shortcuts. API is slightly different but still compatible with current API
• eval is used because some plugins need to be fully loaded to get the shortcuts working
• Documentation is not updated :)

[Setsugennoao]

Can this be reviewed?

[Ichunjo]

yes