Support for Server::start(host, port, callback, OnError)

[softwareCobbler]

dap::net::Server::start right now always binds to "localhost", which is a fine default; but I ran into trying to build this into a javaagent, to be used on a JVM inside a docker container (so debug client is running on host, cppdap is in a container). Apparently, docker container's port forwarding from host<->container requires the applications inside the container to be listening to 0.0.0.0.

Easy fix on the surface -- add an overload that accepts const char* host -- curious if this has drawbacks I don't see, or there is already a built-in solution I am overlooking.