doc: convert the documentation to the block format

The syntax overview no longer describes a line-based format, since that
is not what the rest of the documentation shows.  It now covers the
grammar, the two naming conventions, the nine aliases, and the leading
'-' on a path, and it says plainly that both formats are still read and
told apart per file by content.  Without that, a reader with an
existing configuration is left wondering what happened to it.

service-opts.md was a list of modifiers to place between a directive
and its command, so it needed rewriting rather than translating: there
are no positions left to describe.  It is now grouped by what the
settings do.

conditions.md needed correcting.  It presented '!' as a condition
prefix alongside '~'.  It is neither a condition nor a negation, it is
a flag on the block that means one thing on a service and another on a
run or task, so it is spelled reload-signal and required here, and the
page maps the old form to both.

Two things the pages claimed are not true.  The kill delay range is
1-300, not 1-60, and stop and reload scripts are no longer run without
a timeout.

ChangeLog.md keeps its line-based examples.  Those sit in historical
release entries, and rewriting them in a syntax that did not exist at
the time would misdate the format.

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

doc/config/templating.md

@@ -5,15 +5,19 @@ Finit comes with rudimentary support for templating, similar to that of
 systemd.  Best illustrated with an example:
 
     $ initctl show avahi-autoipd@
-    service :%i avahi-autoipd --syslog %i -- ZeroConf for %i
+    service avahi-autoipd:%i {
+        description = "ZeroConf for %i"
+        command     = "avahi-autoipd --syslog %i"
+    }
 
 To enable ZeroConf for, e.g., `eth0`, use
 
     $ initctl enable avahi-autoipd@eth0.conf
 
 The enabled symlink will be set up to `avahi-autoipd@.conf` and every
-instance of `%i` will in the instantiated directive be replaced with
-`eth0`.  Inspect the resulting instantiated template with `initctl show
+instance of `%i` will be replaced with `eth0` before the file is
+parsed, so it works in the block title, in any value, and in the
+command line alike.  Inspect the resulting instantiated template with `initctl show
 avahi-autoipd:eth0` and check the status of a running instance with:
 
 ```