Fix CEUndoManager grouping

[hi2gage]

Description

Fixes #68

DelegatedUndoManager does not override

func beginUndoGrouping()
func endUndoGrouping()

so calling

textView.undoManager?.beginUndoGrouping()

here and here does not undo as group as expected.

I also updated the names to match between the CEUndoManager and UndoManager.

Related Issues

• 🐞 DelegatedUndoManager undo groups not working as expected #68

Checklist

• I read and understood the contributing guide as well as the code of conduct
• The issues this PR addresses are related to each other
• My changes generate no new warnings
• My code builds and runs on my machine
• My changes are all related to the related issue above
• I documented my code

Screenshots

Before:

CEUndoManager_before.mov

After:

CEUndoManager_after.mov

[austincondiff]

Nice catch, looks good!