Add reshape back

[visr]

In b81c7bc a reshape method very similar to this got added. This was piracy for the case that axs was an empty tuple. This was reported in #193, and this PR implements the original suggestion. Instead in #194 the reshape method was removed entirely since it seemed to serve no purpose other that avoiding issues with OffsetArrays.

Now I am running into

MethodError: no method matching reshape(::Vector{Int64}, ::Tuple{ComponentArrays.CombinedAxis{ComponentArrays.Axis{…}, Base.OneTo{…}}})

Being triggered from: https://github.com/JuliaDiff/FiniteDiff.jl/blob/a7eca2d4b73c4de12140d89df7621fcc90d29190/src/jacobians.jl#L422

So now we can reshape onto our own axes:

using ComponentArrays
cv = ComponentVector(; a = [1, 2], b = [3, 4, 5])
reshape(cv, axes(cv))  # -> ComponentVector{Int64}(a = [1, 2], b = [3, 4, 5])

[visr]

I see this has since been fixed by #297.