Make instant gradient adjustable

src/components/instant_gradients.jl

 module InstantGradients
 import StaticArrays: SVector, SMatrix
 import JuMP: @constraint
-import ...Variables: VariableType, duration, qval, bmat_gradient, get_free_variable, set_simple_constraints!, effective_time, make_generic, adjust_internal
+import ...Variables: VariableType, duration, qval, bmat_gradient, get_free_variable, set_simple_constraints!, effective_time, make_generic, adjust_internal, adjustable
 import ...BuildSequences: global_model
 import ..AbstractTypes: EventComponent, GradientWaveform
 
@@ -70,6 +70,8 @@ bmat_gradient(::InstantGradient, qstart=nothing) = zero(SMatrix{3, 3, Float64, 3
 
 make_generic(ig::InstantGradient) = ig
 
+adjustable(::InstantGradient) = :gradient
+
 function adjust_internal(ig::InstantGradient1D; orientation=nothing, scale=1., rotation=nothing)
     if !isnothing(orientation) && !isnothing(rotation)
         error("Cannot set both the gradient orientation and rotation.")