Make min and max values nullable

Signed-off-by: James Tasker <james_tasker1@hotmail.com>
Refactor SkinDisplay to give access to skin

Signed-off-by: James Tasker <james_tasker1@hotmail.com>
Add newlines before meter and measure names

Signed-off-by: James Tasker <james_tasker1@hotmail.com>
Make meters draggable in SkinDisplay

Signed-off-by: James Tasker <james_tasker1@hotmail.com>