Ahem. Revert "Revert "Change remaining #mw-mf-header occurrences to .header""

This reverts commit dd3408381edac77f90ba6163a98d7b91e8087558

Change-Id: Ie33cf2c9fcf0c066ada154f0fc45b3be4507b1d4
Merge "Ahem. Revert "Revert "Change remaining #mw-mf-header occurrences to .header"""