Add a 'monitor' verb to the udisks command

Add a 'monitor' verb to the udisks command

If we run these commands

 # mkfs.vfat -n "foo" /dev/mmcblk0p1
 mkfs.vfat 3.0.9 (31 Jan 2010)
 # mount /dev/mmcblk0p1 /media/Foo5/
 # umount /media/Foo5
 # dd if=/dev/zero of=/dev/mmcblk0p1 bs=512 count=100
 100+0 records in
 100+0 records out
 51200 bytes (51 kB) copied, 0.0327893 s, 1.6 MB/s

then we get this output

 $ udisks monitor
 Monitoring the udisks daemon. Press Ctrl+C to exit.
 17:44:08.566: The udisks-daemon is running (name-owner :1.267).
 17:44:15.418: /org/freedesktop/UDisks/devices/mmcblk0p1: Received signal org.freedesktop.UDisks.LinuxSysfsDevice::UEvent (b'change',)
 17:44:15.419: /org/freedesktop/UDisks/devices/mmcblk0p1: Added interface org.freedesktop.UDisks.BlockDevice.Probed
 17:44:15.420: /org/freedesktop/UDisks/devices/mmcblk0p1: Added interface org.freedesktop.UDisks.Filesystem
 17:44:15.421: /org/freedesktop/UDisks/devices/mmcblk0p1: org.freedesktop.UDisks.BlockDevice: Properties Changed
   Symlinks:             /dev/block/179:1
                         /dev/disk/by-id/mmc-SD01G_0x50882907-part1
                         /dev/disk/by-path/pci-0000:05:00.2-part1
                         /dev/disk/by-uuid/E2F3-2C42
                         /dev/disk/by-label/foo
 17:44:24.466: /org/freedesktop/UDisks/devices/mmcblk0p1: org.freedesktop.UDisks.Filesystem: Properties Changed
   MountPoint:           /media/Foo5
 17:44:29.582: /org/freedesktop/UDisks/devices/mmcblk0p1: org.freedesktop.UDisks.Filesystem: Properties Changed
   MountPoint:
 17:44:34.586: /org/freedesktop/UDisks/devices/mmcblk0p1: Received signal org.freedesktop.UDisks.LinuxSysfsDevice::UEvent (b'change',)
 17:44:34.589: /org/freedesktop/UDisks/devices/mmcblk0p1: Removed interface org.freedesktop.UDisks.BlockDevice.Probed
 17:44:34.589: /org/freedesktop/UDisks/devices/mmcblk0p1: Removed interface org.freedesktop.UDisks.Filesystem
 17:44:34.589: /org/freedesktop/UDisks/devices/mmcblk0p1: org.freedesktop.UDisks.BlockDevice: Properties Changed
   Symlinks:             /dev/block/179:1
                         /dev/disk/by-id/mmc-SD01G_0x50882907-part1
                         /dev/disk/by-path/pci-0000:05:00.2-part1

which is actually very nice.

Signed-off-by: David Zeuthen <davidz@redhat.com>