This is a work in progress for a full implementation of non-abelian fusion rules in Sectors. It also contains several patches on other components of Sectors. A core aspect is that the dependency order between GradedAxes and Sectors has been reversed: Sectors now depends on GradedAxes.

To do:

• implement fusion rules for CategoryProduct
• implement SymmetryStyle trait with values AbelianGroup, NonAbelianGroup and NonGroupSymmetry

To be decided:

• type return for c1 ⊗ c2: either always a GradedUnitRange or a GradedUnitRange or a Category depending on SymmetryStyle
• whether to keep SU2 and SU{2}.
• whether to implement SU(N) fusion rules or add dependency / fork SUNRepresentations.jl

Decisions:

• c1 ⊗ c2: return type depends on SymmetryStyle
• work on replacing SU2 with SU{2} and try to have a half-integer interface specific to SU{2}

Long term: how to handle braiding for fermions and anyons.