Body background image overlay controls not working consistently

[rramo012]

Depending on the theme options, it's possible that a user has a palette background and an overlay background color set on the body. In this case the palette background class takes precedence and breaks the overlay affect.

Its preferable that we prevent the conflict from existing, but to solve the immediate problem I'll increased the importance of the overlay styles to override the palette background.

[rramo012]

b3c7ef6