Argument type-aware printing for Symbolic terms

[GeorgeR227]

I would want to improve the appearance of my symbolic expression outputs by:

• Removing any module scoping
• Adding some useful input type information to otherwise generic functions

Could we edit the symbolic term printing to allow for these?

Currently the output looks like,

julia> Δ(x) + 2Δ(y)
2Catlab.Theories.Δ(y) + Catlab.Theories.Δ(x)

where this function scope isn't even correct in this case.

I would want it to appear more like,

julia> Δ(x) + 2Δ(y)
2Δ₁(y) + Δ₁(x)

where the labeling on the functions come from the types of the input variables. I'd much prefer this latter output since I feel it is much cleaner to read and more informative.