GPII-1015: Inverted colours of headers

Changed the colours of the headers to be dark on light. This will keep things consistent across the interface and reduce viewing issues in contrast modes.

Note that there are a lot of styling and markup inconsistencies. However, these were out of scope to address in this change.
GPII-1015: Adjusted more header styles.
GPII-1015: Adjustments to headers for PCP
GPII-1015: Added hack to address header height

Added a hack to address the 6px short headers in the PCP. A proper fix directly targeting the anomaly should replace this hack.
GPII-1015: Fixed gpii-pcp class

Had added it to the id instead of to the class attribute.
GPII-1015: combining duplicate styles
GPII-1015: Added display table to header container

Removed the hack from the previous commit and replaced by using display: table styling on the parent container.
GPII-1015: Removed unused class
Merge pull request #83 from jobara/GPII-1015

GPII-1015: Invert header colours