Throw informative error when parsing reference sets in macros

[odow]

Closes #3652

Error from #3652 is now:

julia> using JuMP

julia> model = Model()
A JuMP Model
Feasibility problem with:
Variables: 0
Model mode: AUTOMATIC
CachingOptimizer state: NO_OPTIMIZER
Solver name: No optimizer attached.

julia> @variable(model, a, Int)
a

julia> @variable(model, b[1:a], Int) 
ERROR: At REPL[67]:1: `@variable(model, b[1:a], Int)`: unexpected error parsing reference set: 1:a
Stacktrace:
 [1] error(::String, ::String, ::Expr)
   @ Base ./error.jl:44
 [2] (::JuMP.Containers.var"#error_fn#98"{String})(::String, ::Vararg{Any})
   @ JuMP.Containers ~/.julia/dev/JuMP/src/Containers/macro.jl:315
 [3] macro expansion
   @ ~/.julia/dev/JuMP/src/Containers/macro.jl:92 [inlined]
 [4] macro expansion
   @ ~/.julia/dev/JuMP/src/macros.jl:375 [inlined]
 [5] top-level scope
   @ REPL[67]:1

caused by: MethodError: no method matching (::Colon)(::Int64, ::VariableRef)

Closest candidates are:
  (::Colon)(::T, ::Any, ::T) where T<:Real
   @ Base range.jl:50
  (::Colon)(::A, ::Any, ::C) where {A<:Real, C<:Real}
   @ Base range.jl:10
  (::Colon)(::T, ::Any, ::T) where T
   @ Base range.jl:49
  ...

Stacktrace:
 [1] macro expansion
   @ ~/.julia/dev/JuMP/src/Containers/macro.jl:90 [inlined]
 [2] macro expansion
   @ ~/.julia/dev/JuMP/src/macros.jl:375 [inlined]
 [3] top-level scope
   @ REPL[67]:1

cc @LebedevRI

[LebedevRI]

Nice! Thank you!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b026f67) 98.28% compared to head (f90845f) 98.28%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3653   +/-   ##
=======================================
  Coverage   98.28%   98.28%           
=======================================
  Files          43       43           
  Lines        5640     5650   +10     
=======================================
+ Hits         5543     5553   +10     
  Misses         97       97           

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