Initial patch for USB tracking using inotify

Currentlty, USB connect/disconnect events are triggered using usb_moded.
But usb_moded changes are not ready and also, this mechanism can avoid a
dependency on usb_moded. This mechanism would use inotify to keep track
of the devices created (/dev/ttyGS1) and appropriately signal the
plugins with the connectivityChanged() signal

Signed-off-by: Sateesh Kavuri <sateesh.kavuri@gmail.com>
Added usbNodeExists() method to check if the USB device exists

This method will be useful when msyncd starts and wants to check if the
USB device node (default=/dev/ttyGS1) exists or not

Signed-off-by: Sateesh Kavuri <sateesh.kavuri@gmail.com>
Initial integration of TransportTracker and USBInotify

Signed-off-by: Sateesh Kavuri <sateesh.kavuri@gmail.com>
Added usb node monitoring using QFileSystemWatcher

Using inotify would pretty much boil down to re-implementing
QFileSystemWatcher. Instead, added a watch to '/dev' and would check if
the node /dev/ttyGS1 is created/removed by using QFile API. This is much
simpler and would work just fine. Since the device /dev/ttyGS1 would be
created only in (ex-)ovisuite mode, there would not be any need for
USBModedProxy anymore.

Signed-off-by: Sateesh Kavuri <sateesh.kavuri@gmail.com>