Resolve DataStructures v0.19 deprecations

[lukem12345]

Updating local versions of GATlab, Compose, and Catlab to use DataStructures v0.19 reveals deprecation warnings when using the enqueue! and dequeue! operations on DataStructures.jl Queues. The new usage pattern as suggested by the warnings is to use push! and popfirst! from Base.

┌ Warning: `enqueue!(q::Queue, x)` is deprecated, use `Base.push!(q, x)` instead.
│   caller = connected_component_projection_bfs(g::Catlab.Graphs.BasicGraphs.Graph) at GraphCategories.jl:31
└ @ Core ~/.julia/packages/Catlab/7kAcA/src/categorical_algebra/setcats/GraphCategories.jl:31
┌ Warning: `dequeue!(q::Queue)` is deprecated, use `Base.popfirst!(q)` instead.
│   caller = connected_component_projection_bfs(g::Catlab.Graphs.BasicGraphs.Graph) at GraphCategories.jl:33
└ @ Core ~/.julia/packages/Catlab/7kAcA/src/categorical_algebra/setcats/GraphCategories.jl:33
┌ Warning: `enqueue!(q::Queue, x)` is deprecated, use `Base.push!(q, x)` instead.
│   caller = connected_component_projection_bfs(g::Catlab.Graphs.BasicGraphs.Graph) at GraphCategories.jl:36
└ @ Core ~/.julia/packages/Catlab/7kAcA/src/categorical_algebra/setcats/GraphCategories.jl:36

[lukem12345]

This would need to be merged pending the upstream PRs/ issues here: