Use proper cursor image for output view right of text

Fixes #763.
File browser: Dispose all children on collapse

Previously we kept the children which had been expanded, as these had an associated record for tracking file system changes and SCM info.

However, when expanding we weren’t actually re-using the item from the cached record, so not only was this wasteful, but it caused a problem because we effectively created a new item but used the old record with the old item, and while the two items would compare is equal when using isEqualTo:, they didn’t have the same memory address, so the outline view would not consider them equal, and would thus not react on reload requests when using the older item.
Add memory address to FSItem description

Since table views use the memory address, and these items are for use in table views, it’s useful to see the address when printing an item.
Reload updated folders on reactivation

This is done by stat’ing all visible folders and is a fallback for when fs-events is not working (e.g. network file systems).
Move instance data to implementation file
Checkin release notes