Broken Julia LTS v1.0 Support

[mehalter]

A recent change (I believe it is the UWD support in Graphviz) to Catlab has broken support of Julia v1.0 LTS. I think as a project we should make sure that code supports not just the latest versions, but make sure it supports whatever the latest LTS is.

stack trace:

julia> using Catlab
[ Info: Precompiling Catlab [134e5e36-593f-5add-ad60-77f754baafbe]
ERROR: LoadError: LoadError: LoadError: syntax: invalid function name "Graph <: Expression"
Stacktrace:
 [1] include at ./boot.jl:317 [inlined]
 [2] include_relative(::Module, ::String) at ./loading.jl:1044
 [3] include at ./sysimg.jl:29 [inlined]
 [4] include(::String) at /home/micah/TEST/env/.julia/packages/Catlab/z8n1h/src/graphics/Graphics.jl:1
 [5] top-level scope at none:0
 [6] include at ./boot.jl:317 [inlined]
 [7] include_relative(::Module, ::String) at ./loading.jl:1044
 [8] include at ./sysimg.jl:29 [inlined]
 [9] include(::String) at /home/micah/TEST/env/.julia/packages/Catlab/z8n1h/src/Catlab.jl:1
 [10] top-level scope at none:0
 [11] include at ./boot.jl:317 [inlined]
 [12] include_relative(::Module, ::String) at ./loading.jl:1044
 [13] include(::Module, ::String) at ./sysimg.jl:29
 [14] top-level scope at none:2
 [15] eval at ./boot.jl:319 [inlined]
 [16] eval(::Expr) at ./client.jl:393
 [17] top-level scope at ./none:3
in expression starting at /home/micah/TEST/env/.julia/packages/Catlab/z8n1h/src/graphics/Graphviz.jl:43
in expression starting at /home/micah/TEST/env/.julia/packages/Catlab/z8n1h/src/graphics/Graphics.jl:7
in expression starting at /home/micah/TEST/env/.julia/packages/Catlab/z8n1h/src/Catlab.jl:7
ERROR: Failed to precompile Catlab [134e5e36-593f-5add-ad60-77f754baafbe] to /home/micah/TEST/env/.julia/compiled/v1.0/Catlab/fBQ1G.ji.
Stacktrace:
 [1] error(::String) at ./error.jl:33
 [2] compilecache(::Base.PkgId, ::String) at ./loading.jl:1203
 [3] _require(::Base.PkgId) at ./loading.jl:960
 [4] require(::Base.PkgId) at ./loading.jl:858
 [5] require(::Module, ::Symbol) at ./loading.jl:853

[epatters]

I had disabled the CI tests for 1.0 a while ago, because the manifest file wasn't compatible with Julia < 1.3, but that won't be a problem anymore. We can re-enable tests on 1.0 and fix the problem (hopefully).

[epatters]

The issue is that extensions to Base.@kw_def have not been backported to 1.0 via Compat: JuliaLang/Compat.jl#638.

To support 1.0, we'll have to switch back to Parameters.jl. Sigh.