Use sensorfw for ambient light and proximity sensor input

Tracks sensord D-Bus name on system bus to detect availability
of the sensors API.

While the D-Bus name is not reserved, ALS and PS enable states
are cached internally within MCE. When sensord startup / restart
is detected the cached state is used for opening sensor sessions
as needed.

[mce] Use sensorfw for ambient light and proximity sensor input
Set proximity sensor default value to COVER_OPEN

Using zero (=COVER_CLOSED) combined with failure to get data from the
proximity sensor caused misfiring proximity blanking during phone calls.
Merge pull request #70 from spiiroin/default_proximity

Set proximity sensor default value to COVER_OPEN
Merge pull request #69 from spiiroin/use_sensorfw

Use sensorfw for ambient light and proximity sensor input
Fix memory leak

Pending call was left with an extra reference.
Fix dbus name owner monitoring

The NameOwnerChanged signal content is
* arg0 the dbus name that has changed ownership
* arg1 the private dbus name of the previous owner
* arg2 the private dbus name of the current owner

To catch loss of name owner, we want to receive signals
where arg0 is the name we are interested in and arg2 is
an empty string.

Also fixes memory leak in fake_owner_gone()
Do not suspend if ipc with lipstick fails

Copy paste bug in state transition.
Merge pull request #73 from spiiroin/fix_display_stm

Do not suspend if ipc with lipstick fails
Merge pull request #71 from spiiroin/pending_call_leak

Fix memory leak
Merge pull request #72 from spiiroin/name_owner_lost_tracking

Fix dbus name owner monitoring
Bump mce version to 1.15.0