input: Use GdkDeviceManager to monitor devices

Instead of an XI2 filter.
input: Ignore audio/video devices earlier
input: Always enable debug by default
input: Use GdkDevice to sort through devices

Rather than using X APIs
input: Remove X11 dependency
input: Re-enable the BluetoothInput test program
input: Remove unused variable
input: Make code actually work

Gather the presence or absence of mouse or keyboard correctly,
and send out the signals.
input: Add debug version
lib: Remove unnecessary linefeeds from debug output
lib: Don't forget to set the DiscoverableTimeout too

Otherwise the visibility will reset after 3 minutes by default.
wizard: Remove unused label_fixed

It was added but never actually used.
wizard: Fix PIN database not being used

We would get data from the PIN code database, but never actually
set that to be the selected PIN code.
wizard: Only show PIN page for random pin codes

When pincode_callback() is called, only show the PIN page for
random PIN codes, otherwise we'll show the stock, unmodified
page asking to enter 123456 for device Foobar.
wizard: Don't try to connect in a busy loop

If the device wasn't quite ready, we would try to connect to it
in a busy loop (as an error was returned immediately when trying to
connect). Now we wait 500 msecs between connection.