WIP: Refactoring dnsfoam

Summary

dnsFoam is refactored, and its external behaviour is verified through dnsFoam/boxTurb16 tutorial.

diff all the fields of {enstrophy,graphs,p,phi,U} from the original tutorial, and refactored dnsfoam yielded no change.

Resolved bugs (If applicable)

N/A

Details of new models (If applicable)

N/A

Risks

N/A