Add on-hover selection on Board/Library manager

User testing on skilled devs showed that "buttons appear on click" behaviour is far from being understood.
Accessibility features (like moving with Arrow keys) should be untouched.

Author: facchinm

app/src/cc/arduino/contributions/ui/InstallerJDialog.java

@@ -43,6 +43,8 @@
 import java.awt.event.FocusListener;
 import java.awt.event.KeyEvent;
 import java.awt.event.WindowEvent;
+import java.awt.event.MouseEvent;
+import java.awt.event.MouseMotionListener;
 import java.util.function.Predicate;
 import java.util.stream.Stream;
 
@@ -167,6 +169,15 @@ public void keyReleased(KeyEvent keyEvent) {
       }
     });
 
+    contribTable.addMouseMotionListener(new MouseMotionListener() {
+
+        public void mouseDragged(MouseEvent e) {}
+
+        public void mouseMoved(MouseEvent e) {
+            contribTable.editCellAt(contribTable.rowAtPoint(e.getPoint()), 0);
+        }
+    });
+
     {
       TableColumnModel tcm = contribTable.getColumnModel();
       TableColumn col = tcm.getColumn(0);