Add verbose = false option

[TorkelE]

When loading a large number of models, it could be nice to add an option to turn off printing like

Parsing parameters...done
Creating parameters...done
Parsing species...done
Creating species...done
Creating species and parameters for evaluating expressions...done
Parsing and adding reactions...done
Parsing groups...done

Happy to add at some point, should be straightforward to change

print("Creating species and parameters for evaluating expressions..."

to

verbose && print("Creating species and parameters for evaluating expressions..."

[ChrisRackauckas]

Yeah this repo probably just needs a verbose. Though we should at some point make it easier to set globally, some related discussion in SciML/SciMLBase.jl#962

[isaacsas]

@TorkelE a PR for this would certainly be welcome.

We'll likely need some updates here after Catalyst 15 anyways, so at that time perhaps we can do a bit of a refresh. I wanted to fix up species creation for networks defined via stoichiometric matrices.