#1694 The edited indicator appears when a track selection changes

[musewhirl]

It's been around a while on master but I don't recall seeing it back in v18.12. It doesn't harm anything except suggesting a save when it often might not be necessary.

Steps to reproduce:

1. Open an existing session
2. Select a different track
3. The edited indicator (an asterisk in my case) shows up in the window bar, but nothing has been edited
4. In addition, closing RG does not warn of any changes to be saved

[Ted Felix]

There are two key routines related to this:

• RosegardenDocument::setModified()
• RosegardenDocument::slotDocumentModified()

I've been erring toward marking as modified, and yeah, it's a bit overzealous. There are numerous other situations where the modified flag is set but shouldn't be. This is tangled up with the need to inform the UI that there have been changes and it needs to update itself. A review and redesign is definitely needed so there is a clear separation between UI updates with and without setting the document modified flag/star.

The fact that a prompt to save is not triggered for a "non-change" means we've got partial support for this already in there. But it needs work.