fix yoneda_cache support for DynamicACSets

[aaguinal]

I created a DynamicAcset using the following code:

@present SchAi2Thor(FreeSchema) begin
  ## Objects
  RoboGripper::Ob
  Thing::Ob  # all Null ∪ objects

  ## Attributes for Thing
  Label::AttrType
  IsOpen::AttrType
  IsBroken::AttrType
  IsCooked::AttrType
  IsSliced::AttrType
  IsToggled::AttrType
  IsDirty::AttrType
  IsFilledWithLiquid::AttrType
  IsUsedUp::AttrType

  thing_has_label::Attr(Thing, Label)
  thing_is_open::Attr(Thing, IsOpen)
  thing_is_broken::Attr(Thing, IsBroken)
  thing_is_cooked::Attr(Thing, IsCooked)
  thing_is_sliced::Attr(Thing, IsSliced)
  thing_is_toggled::Attr(Thing, IsToggled)
  thing_is_dirty::Attr(Thing, IsDirty)
  thing_is_filled_with_liquid::Attr(Thing, IsFilledWithLiquid)
  thing_is_used_up::Attr(Thing, IsUsedUp)

  PositionX::AttrType
  PositionY::AttrType
  PositionZ::AttrType
  thing_has_positionX::Attr(Thing, PositionX)
  thing_has_positionY::Attr(Thing, PositionY)
  thing_has_positionZ::Attr(Thing, PositionZ)

  ## Relations
  PartOfRel::Ob
  InRel::Ob  # Q: How do I enforce that things of a particular type can only be inside other things of certain types?

  is_holding::Hom(RoboGripper, Thing)
  is_part_of_l::Hom(PartOfRel, Thing)
  is_part_of_r::Hom(PartOfRel, Thing)
  is_in_l::Hom(InRel, Thing)
  is_in_r::Hom(InRel, Thing)
end

# specify types for attributes
const type_assignment = Dict(
  :Label => String,
  :IsOpen => Bool,
  :IsBroken => Bool,
  :IsCooked => Bool,
  :IsSliced => Bool,
  :IsToggled => Bool,
  :IsDirty => Bool,
  :IsFilledWithLiquid => Bool,
  :IsUsedUp => Bool,
  :PositionX => Float64,
  :PositionY => Float64,
  :PositionZ => Float64
)

# create dynamic acset object
const Ai2Thor = DynamicACSet("Ai2Thor", SchAi2Thor;
  type_assignment=type_assignment)

When I attempt to compute the representables for that ACSet, I get the following error:

ERROR: MethodError: no method matching yoneda_cache(::DynamicACSet)

Closest candidates are:
  yoneda_cache(::Type)
   @ AlgebraicRewriting ~/.julia/packages/AlgebraicRewriting/W29UX/src/rewrite/Representable.jl:41
  yoneda_cache(::Type, ::Any; clear, cache)
   @ AlgebraicRewriting ~/.julia/packages/AlgebraicRewriting/W29UX/src/rewrite/Representable.jl:41

Stacktrace:
 [1] top-level scope
   @ ~/Documents/Git/ai2thor-cset-experiments/julia/Ai2thorCsetProject/Ai2ThorWorld-Rules-CR.jl:114