man: import org.freedesktop.machine1(3) from the wiki

man: import org.freedesktop.machine1(3) from the wiki

The wiki was primarily describing the D-Bus API, but it also had a large
introduction to the daemon functionality. I moved that latter part into
the page that describes the daemon, and the API description into the new
page.

This is mostly a straighforward import. Apart from some required formatting
changes, I removed obvious repetitions, and made tiny grammar and typo fixes
where I noticed them. The goal is not to have a perfect text immediately.

<interfacename>org.foo.bar</interface> is used for interface names,
<function>function()</function> for methods, and <function>signal</function>
(no parentheses) for signal names. In D-Bus, signals are similar to methods,
and docbook doesn't have a nice tag for them.