Allow dbus handler to listen all signals from an interface

Adding signal handler with NULL name is now allowed and means that
any signal with non-null member attribute is matched.

Replace dbus_message_is_xxx predicates in signal filter with custom
code that understands the special meaning NULL values now have.
Block late suspend while bluetooth activity is seen on D-Bus

Add plugin for monitoring bluetooth activity on D-Bus.

Any D-Bus signals from bluez are taken as bluetooth activity and late
suspend is blocked until no more signals are seen for 5 seconds. This
should allow time for bluetooth related processing to happen without
the device falling to late suspend too early.

[mce] Block late suspend while bluetooth activity is seen on D-Bus. Fixes JB#18124
Count org.bluez.Audio signals as bluetooth activity too
Merge pull request #155 from spiiroin/bt_activity_blocks_suspend

Bluetooth activity blocks suspend