Use DBUS to detect media insertion or removal

This patch upgrades libmyth/mediamonitor-unix.cpp to use the DBus
message bus to detect changes to removable media.

 Currently, to detect the insertion of USB drives and key-disks the code
requires changes to udev configuration files, needing root permission,
and is very Linux specific. This patch uses UDisks
http://hal.freedesktop.org/docs/udisks/ messages which is a standard
across many *nix systems. In addition the code is simpler, provides more
information on the devices and most importantly needs no changes to
system configuration. If the QT DBus module is not present the code will
fallback to the current system.

Closes #9519

Signed-off-by: Stuart Morgan <smorgan@mythtv.org>

Author: Lawrence Rust

mythtv/libs/libmyth/libmyth.pro

@@ -144,6 +144,7 @@ using_pulse {
 unix:!cygwin {
     SOURCES += mediamonitor-unix.cpp
     HEADERS += mediamonitor-unix.h
+    using_qtdbus: CONFIG += qdbus
 }
 
 linux:DEFINES += linux