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
I played a bit more on the issue of the missing 6px. It seems if we add "display: table" onto the parent container for the header image and text (https://github.com/jobara/prefsEditors/blob/GPII-1015/src/shared/adjusters/html/increaseSizeTemplatePCP.html#L1), where both of them have "display" prop set to "table" or "table-cell", the dislocated lines can be fixed.