Ensure SetOption is only callable if the server has not been started yet

[belak]

Optionally, make a copy when calling makeConfig so the running server config can't be modified.

[progrium]

Even better.

[hloeffler]

+1 for copy, will help if multiple servers are used, with different config.
and please first add test for it

[progrium]

Looks like we could still use a check if it's running in SetOption to bail if it's too late.

[josegonzalez]

@progrium Do we want to use the srv.state idea @belak initially had in PR #23?

[progrium]

Might be good to introduce.