[3.2.12] make package groups invisible by default

[LisaAlmarode]

This is controlled by a preference, the preference should be off for now.

Also the pane widths of the project browser when it starts up with packageGroupsVisible: false should be balanced; the default should have the most likely arrangement. We do not need that much space for the package names (not even rowan package names are that long).

[ericwinger]

Should default to non-visible now in the preferences file and the panes are more balanced. Open to further sizing adjustments if needed.