Change yup, ydown getters to return pointers
Add 3D tensors for ints
Add methods to DataFile in order to use python "with" keyword
Add FCI example
Merge branch 'fci' of git@github.com:boutproject/BOUT-dev into fci

* 'fci' of git@github.com:boutproject/BOUT-dev:
  Changes to Solver classes

Conflicts:
	src/field/field3d.cxx
Almost working interpolation