Fix #186: allow continuation character in .conf files

This change makes it possible to use the standard continuation character
in .conf files.  For example:

    service [23456]     \
         log:stderr     \
         <!pid/foo>     \
         bar            \
         -- This is the bar service, it depends on foo # comment that's dropped

Notice the additional support for comments on .conf lines.  If you use
the comment character today you must change to escape it.  Like this:

    service :2 foo -- Foo \#2

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

doc/config.md

@@ -1,5 +1,5 @@
-Configuration
-=============
+Finit Configuration
+===================
 
 * [Introduction](#introduction)
   * [Environment Variables](#environment-variables)
@@ -297,6 +297,25 @@ Linux kernel, or the name is misspelled.
 Configuration File Syntax
 -------------------------
 
+The file format is line based, empty lines and comments, lines starting
+with `#`, are ignored.  A configuration directive starts with a keyword
+followed by a space and the rest of the line is treated as the value.
+
+As of Finit v4.4, configuration directives can be broken up in multiple
+lines using the continuation character `\`, and trailing comments are
+also allowed.  Example:
+
+```aconf
+# Escape \# chars if you want them literal in, e.g., descriptions
+service name:sysklogd [S123456789]   \
+    env:-/etc/default/sysklogd       \
+    syslogd -F $SYSLOGD_ARGS         \
+    -- System log daemon \# 1   # Comments allowed now
+```
+
+The .conf files `/etc/finit.conf` and `/etc/finit.d/*` support the
+following directives:
+
 ### Hostname
 
 **Syntax:** `host <NAME>`, or `hostname <NAME>`