doc: fix back-references and stale claims left by the conversion

Reference sections kept pointing at the line-based format they no longer
document.  `sysv` and `task` sent the reader to Services for "<COND>",
the cgroups chapter opened by listing three legacy directives and then
explained further down that only two of them exist here, and the logging
chapter still gave "log:prio:facility.level,tag:ident" as the full
syntax.

Some claims were wrong independent of the format:

  - a sysv is a supervised daemon, grouped with service in
    SVC_TYPE_DAEMON, not a variation on task
  - restart-max has no upper bound of 255, or any other
  - the built-in rescue fallback runs in 12345789, not 12345
  - conditional loading quotes system/10-hotplug.conf, not
    system/hotplug.conf
  - the key spells conflicts, not conflict
  - the built-in getty no longer wants TERM last, it is a key

`if` takes either a service name or, in angle brackets, a condition,
decided in svc_ifthen().  Only the examples showed this, so it is now
said.

Terminology follows the split index.md already draws: a block is the new
format, a stanza the line-based one.

src/rescue.conf was still line-based, missed because it sits in src/
rather than system/ or contrib/.

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

doc/example.md

@@ -132,7 +132,7 @@ tty tty3 {
 #tty console { runlevel = "12345"  device = "@console"  noclear = true  nologin = true }
 ```
 
-The `service` stanza, as well as `task`, `run` and others are described in
+The `service` block, as well as `task`, `run` and others are described in
 full in the [Services Syntax](config/services.md) section.
 
 Here's a quick overview of some of the most common components needed to start