improve generated code for import

This improves the generated code for loading vector export and scalar export.

Expected but missing fields (previously didn't exist or were @exportoffd) no longer error immediately. It is up to the constructor of the e.g. Particle type (or importconstruct) to implement a sensible default.

In addition to that this change improves load time with 20k particles by x5-20 locally for me.

This should make some of the fix_import functions obsolete.

This breaks the matching done in add_scalar_fallback. This could now be done in importconstruct or alternatively adapt the matching. add_vector_fallback will also no longer match. An importconstruct would be easiest e.g. InPartS.ExportUtils.importconstruct(t::Type{<:MotileCell}; ∫Fax=NaN, kwargs...) = t(; ∫Fax, kwargs...)

Compat with all cell models and fix_import will need to be ensured.

ext/HDF5Ext.jl

@@ -5,7 +5,7 @@ using InPartS
 
 
 
-struct H5Wrapper{T<:Union{HDF5.File, HDF5.Group}}
+struct H5Wrapper{T<:Union{HDF5.File, HDF5.Group}} <: AbstractDict{String, Any}
     handle::T
 end
 
@@ -72,4 +72,4 @@ Base.length(h5w::H5Wrapper) = length(h5w.handle)
 # more efficient readdict
 InPartS.readdict(h5w::H5Wrapper; kwargs...) = read(h5w.handle)
 
-end
\ No newline at end of file
+end