Fix #235: support for overriding /etc/finit.conf and /etc/finit.d

This change adds support for a new command line option finit.config=PATH
which can be used to tell Finit to start with /etc/factory.conf instead
of /etc/finit.conf.

For the complete experience a new top-level configuration file directive
`rcsd PATH` has aslo been added.  It in turn can be used by factory.conf
as follows to override /etc/finit.d:

    rcsd /etc/factory.d

Manually verified in myLinux

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/sm.c

@@ -121,7 +121,7 @@ restart:
 
 	switch (sm->state) {
 	case SM_BOOTSTRAP_STATE:
-		dbg("Bootstrapping all services in runlevel S from %s", FINIT_CONF);
+		dbg("Bootstrapping all services in runlevel S from %s", finit_conf);
 		service_step_all(SVC_TYPE_RUNTASK | SVC_TYPE_SERVICE);
 		sm->state = SM_RUNNING_STATE;
 		break;