Add config option for manually started services

Example:
    service manual:yes [2] /usr/sbin/lighttpd -- HTTP Server

Signed-off-by: Robert Andersson <robert.m.andersson@se.atlascopco.com>

docs/config.md

@@ -185,6 +185,12 @@ Syntax
   For a detailed description of conditions, and how to debug them, see
   the [Finit Conditions](conditions.md) document.
 
+  If a service should not be automatically started, it can be configured
+  as manual with the optional `manual` argument. The service can then be
+  started at any time by running `initctl start <service>`.
+
+        manual:yes
+
   The name of a service, shown by the `initctl` tool, defaults to the
   basename of the service executable. It can be changed with the
   optional `name` argument: