[WIP] Use new transformation style in delete and paste

[johnfn]

Refactoring this massive codebase into this new style is... tough.

The more we do it, though, the more awesome multi-cursor becomes. And also, the more consistent our codebase becomes. Which is nice for anyone who wants to add stuff to it. 😉

Todo

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[xconverge]

I don't really see where diff is used in a lot of cases? is there an obvious base class implementation somewhere I am missing? Trying to understand why this is good :)

[johnfn]

@xconverge the diffs are all used in executeCommand in ModeHandler.

Essentially now the way we do cursor position updates is by a diff instead of by an exact location. This is because if you're running a command on lots of cursors in multi-cursor mode, previous inserts could offset your current location, which would invalidate locations you calculated.