Merged config and app packages into one called caddy. Abstracted away caddy startup functionality making it easier to embed Caddy in any Go application and use it as a library. Graceful restart (should) now ensure child starts properly. Now piping a gob bundle to child process so that the child can match up inherited listeners to server address. Much cleanup still to do.

Lots of refinement still needed and runs only on POSIX systems. Windows will not get true graceful restarts (for now), but we will opt for very, very quick forceful restarts. Also, server configs are no longer put into a map; it is critical that they stay ordered so that they can be matched with their sockets in the child process after forking.

This implementation of graceful restarts is probably not perfect, but it is a good start. Lots of details to attend to now.

letsencrypt: Simplify timing mechanism for checking renewals

Conflicts:
	config/letsencrypt/letsencrypt.go

User can specify 'tls off" in Caddyfile to force-disable automatic HTTPS configuration

Also added ServerBlockHostIndex

Also more comments and starting to clean up code

Code is a huge mess; much cleanup to follow.

Conflicts:
	config/config.go

This way, Setup functions have access to the list of hosts that share the server block, and also, if needed for some reason, the index of the server block in the input

startup and shutdown commands should only be executed once per appearance in the Caddyfile (naturally meaning once per server block).

Notice that we support multiple occurrences of startup and shutdown in the same server block by building the callback array incrementally as we parse the Caddyfile, then we append all the callbacks all at once. Quite literally, the OncePerServerBlock function executes only once per server block!

If each server block had only one sync.Once then all directives would refer to it and only the first directive would be able to use it! So this commit changes it to a map of sync.Once instances, keyed by directive. So by creating a new map for every server block, each directive in that block can get its own sync.Once which is exactly what is needed. They won't step on each other this way.