No `OneTo` method for `ZZRingElem`

[mjrodgers]

Apparently we don't have this defined, it causes some problems with some of the combinatorics methods (that have special constructors using OneTo, for instance combinations.

Is there a way for us to extend this method to allow ZZRingElem arguments?

julia> combinations(ZZ(3),ZZ(2))
ERROR: MethodError: no method matching Base.OneTo(::ZZRingElem)

Closest candidates are:
  Base.OneTo(::AbstractRange{T}) where T<:Integer
   @ Base range.jl:468
  Base.OneTo(::T) where T<:Integer
   @ Base range.jl:467

Stacktrace:
 [1] oneto(r::ZZRingElem)
   @ Base ./range.jl:469
 [2] combinations(n::ZZRingElem, k::ZZRingElem; inplace::Bool)
   @ Oscar ~/.julia/dev/Oscar/src/Combinatorics/EnumerativeCombinatorics/combinations.jl:25
 [3] combinations(n::ZZRingElem, k::ZZRingElem)
   @ Oscar ~/.julia/dev/Oscar/src/Combinatorics/EnumerativeCombinatorics/combinations.jl:25
 [4] top-level scope
   @ REPL[19]:1

[fingolfin]

The current code for ranges over ZZRingElem is defined in Nemo.

Probably have to clone the OneTo type in Julia into a ZZOneTo type...

[fingolfin]

@mjrodgers will look into doing this