add/remove_species are no longer supported by Space/World
renamed Model::add_species -> add_species_attribute
implemented apply_species_attributes
apply attributes to a species before creating a new molecule
wrapped apply_species_attributes and get_species in NetworkModel
updated a sample for reaction_reader
renamed get_species -> create_species
for a sample, species_attributes seems better than species_attributes_with_keys
updated a sample in spatiocyte_python
updated a sample for egfrd_python
generalized the expressions parsed in a decorated function
removed an unnecessary member
add egfr sample
added some reaction rules
tentative implementation for a reaction generator
moved generate_reactions from a sample into a library
added more strict check for the object type to a parser
prepared for caching in a species
integrated FirstOrder- and SecondOrder- reaction rules into ReactionRule
removed an useless function from ReactionRule