Colon Case for Arrays

[lrennels]

Add methods to support colons between Timesteps ie.
using Mimi

## Failing Case
@defcomp A begin
    p = Parameter(index = [time, pools])
    v1 = Variable(index = [time, pools])
    v2 = Variable(index = [time])

    function run_timestep(p, v, d, t)
        v.v1[t,:] = p.p[t,:]
        if is_first(t)
            v.v2[t] = 0
        else
            v.v2[t] = sum(v.v1[(t-1):t,:])
        end
    end
end

m = Model()
set_dimension!(m, :time, 1:10)
set_dimension!(m, :pools, 1:3)
add_comp!(m, A)

set_param!(m, :A, :p, fill(1,10,3))

run(m)

## Smaller Case
@efcomp A begin
    p = Parameter(index = [time])
    v = Variable(index = [time])

    function run_timestep(p, v, d, t)
        if is_first(t)
            v.v[t] = p.p[t]
        else
            v.v[t] = sum(p.p[t:t])
            # or v.v[t] = sum(p, p[t-1:t])
        end
    end
end

m = Model()
set_dimension!(m, :time, 1:10)
add_comp!(m, A)

set_param!(m, :A, :p, 1:10)

run(m)

[lrennels]

or even smaller ...

julia> Mimi.FixedTimestep:Mimi.FixedTimestep
ERROR: MethodError: no method matching -(::Type{Mimi.FixedTimestep}, ::Type{Mimi.FixedTimestep})
Closest candidates are:
  -(::Array{DoubleFloats.DoubleFloat{T}, 2}, ::T) where T at /Users/lisarennels/.julia/packages/DoubleFloats/KXG5r/src/extras/misc.jl:62
  -(::Array{DoubleFloats.DoubleFloat{T}, 1}, ::T) where T at /Users/lisarennels/.julia/packages/DoubleFloats/KXG5r/src/extras/misc.jl:56
  -(::Intervals.Interval, ::Any) at /Users/lisarennels/.julia/packages/Intervals/ua9cq/src/interval.jl:297
  ...
Stacktrace:
 [1] (::Colon)(start::Type{Mimi.FixedTimestep}, stop::Type{Mimi.FixedTimestep})
   @ Base ./range.jl:7
 [2] top-level scope
   @ REPL[147]:1