Color picker : No mouse caging in 2D spectrum (leading to loss of tracking is mouse exists then re-enters area)

ROS 0.4.15-dev-140-g8c59705

Color picker : mouse tracking lost if mouse exists and re-enter 2D spectrum

Using the standard color picker (with 2D color spectrum on the right)

• Click on 2D spectrum and mouse the mouse : selected color "follows" mouse cursor
• Keep mouse Lbutton down and exist and re-enter => color tracking is stopped

In Windows XP, as long as Lbutton is down, cursor is "caged" in 2D color spectrum