just copied from bd
implemented libecs::Model in SpatiocyteWorld
combined SpatiocyteWorld to SpatiocyteSimulator
modifed reactant_container_type to product_container_type
implemented add_reaction_rule
added a sample
added functions for registering optional processes.
implemented SpatiocyteWorld::t().
implemented SpatiocyteSimulator::step(const Real&)
fixed the wrong order of arguments when initializing Species.
use the absolute path
check if the model is already initialized or not.
removed unnecessary environment variables from the instruction
wrapped simulator generation into EGFRDWorld
small mods in sample
use -l: for loading shared objects
updated the instruction for full installation