Replace image browse button by making textbox clickable

Signed-off-by: James Tasker <james_tasker1@hotmail.com>
Add ability to change skin's background colour

Signed-off-by: James Tasker <james_tasker1@hotmail.com>
Make skin recalculate its boundaries when a meter changes position or size

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