Fix merging of edits in inline color editor

Some recent changes in cmv4 broke the merging of edits in the inline color editor, so when modifying a color every small change counted as a separate undo. This change fixes it by batching together the color edit and its associated selection change as an operation, which allows CodeMirror's history merging to batch nearby changes together.

I also changed the edit origin from `*InlineColorEditor_xxx` to `+InlineColorEditor_xxx`. This makes it so the history merging only happens for edits that are close to each other. It seems better to let people undo if they pause between changes in the inline color editor, rather than grouping every edit that happens in the color editor into a single undo even if the edits are separated widely in time.