Merge branch 'merge-foundation' into 'develop'

Merge foundation

Integrating latest code from the OF Foundation - main changes:

Lots of renaming/refactoring:
- to retrieve reference from tmp, now need to use tmp.ref() as opposed to tmp()
- fvc::flux function to replace fvc::interpolate(<field>) & mesh.Sf()
- integration of new c++ features: no more spaces between closing template braces, e.g. class1<class2<Type> > becomes class1<class2<Type>>
- DataEntry renamed to Function1

New functionality:
- Updated 6DoF
- fvOptions support in turbulence models

See merge request !33