Revert "Revert "GCS: Remove MyListWidget""

This reverts commit 792a0d800fd30e9989b246094f810582c5c1c1af.

I thought removing MyListWidget (which inherits a class and
does nothing) was breaking the layout, but actually it just
depends on if the tab bar is visible when onConnected occurs.
Qt5: Update style sheets

Since we removed MyListWidget for QListWidget the style sheet
should account for this.