Optionally don't highlight other than the selected text block

[andrelkin]

Currently when a block of text is highlighted and a note is arranged for it any following occurrences of the selected block if any
got colorized the same way.
This may not be the actual intent I believe so at least the current "greedy" highlighting is better off to become optional (and not default for my taste and purposes).

Thanks for a great piece of software program!