Usability, a servivce stopped by a user is stopped, not blocked

The generic term for a non-running service is blocked, but a service may
be blocked for several different reasons.  When a user stops a service
with `initctl stop` the intuitive expected output from `initctl show` is
"stopped" not "blocked".

When the user later restarts the service with `initctl start` it may of
course be blocked due to wrong runlevel or a missing condition.  As can
be expected from the service's configuration.

The rest of the patch refactors the internal API names a bit to reflect
this change.

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

doc/service.md

@@ -14,8 +14,9 @@ state.
 The current state depends on the two following conditions:
 
 * `E`: Service enabled. In order for `E` to be satisfied, the service
-  must be allowed to run in the current runlevel and must not be
-  blocked.  A service may be blocked for several reasons:
+  must be allowed to run in the current runlevel and not be stopped.
+  
+  A service may be stopped, or blocked, for several reasons:
 
   - The user has manually stopped the service using `initctl stop JOB`
   - The program exits immediately. I.e. keeps crashing (make sure to use