Improve examples/var_service READMEs

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

examples/var_service/README

@@ -9,6 +9,15 @@ env - PATH=... <other vars=...> runsvdir /var/service &
 from one of system startup scripts. (Google "man runsvdir" and "man runsv"
 for more info about these tools).
 
+You can try or debug an individual service by running its SERVICE_DIR/run script.
+In this case, its stdout and stderr go to your terminal.
+
+You can also run "runsv SERVICE_DIR", which runs both the service
+and its logger service (SERVICE_DIR/log/run) if logger service exists.
+If logger service exists, the output will go to it instead of the terminal.
+
+"runsvdir DIR" merely runs "runsv SERVICE_DIR" for every subdirectory in DIR.
+
 Some existing examples:
 
 var_service/dhcp_if -
@@ -47,8 +56,8 @@ This even works while fw service runs: if dhcp signals fw to (re)start
 while fw runs, fw will not stop after its execution, but will re-execute once,
 picking up dhcp's new configuration.
 This is achieved very simply by having
-# Make ourself one-shot
-sv o .
+	# Make ourself one-shot
+	sv o .
 at the very beginning of fw/run script, not at the end.
 Therefore, any "sv u /var/run/service/fw" command by any other
 script "undoes" o(ne-shot) command if fw still runs, thus