Add ability to convert tasks or activities to notes

Currently you can convert an activity to a task, or a task to an activity. It would be helpful to also allow converting a task/activity to a note and vice versa.

This would be most useful in cases of importing files from Visio, as you can convert to a note in the import function, however most users find the import coding inconvenient, so prefer to import the text directly and make changes once it is in the normal process editing screen.