Refactor config - split read_config into read_config and resolve_config

Split the read_config function into read_config that ONLY reads the
configuration files but doesn't try to resolve any of the
inheritances, and resolve_config which resolves the inheritance chain
of a given target.  Move them to the bottom of Configure, with the
rest of the helpers.

Have a new small hash table, %target, which will hold the values for
the target the user requested.  This also means that all access to the
current target data can be reduced from '$table{$target}->{key}' to a
mere '$target{key}'.

While we're at it, the old string formatted configurations are getting
obsolete, so they may as well get deprecated entirely.

Reviewed-by: Rich Salz <rsalz@openssl.org>