GPII-1015

Inverted the contrast of the panel headers for the adjuster groups. 

This pull request does not address the inconsistent implementations of the panel headers. It also introduces a hack to ensure that the panel headers heights were the same (for some reason in the PCP they were 6px shorter despite the markup and styling being essentially identical).

http://issues.gpii.net/browse/GPII-1015
The same set of the styling is also applied to span.gpii-preset-button-label from line 1632. Can we combine them to reduce the repetition? Thanks.