p2p: Display P2P peer MAC address if device name is empty.

Display MAC address of a P2P peer in an invitation prompt
message on receiving invitation request from the P2P peer
with empty device name.

Change-Id: Icabeb91d666437746eb5a733ec582849eb7295a5
CRs-Fixed: 506109
Update the color of the expandable volume panel icon

This still retains the old settings icon since it
happens to fit perfectly. Pressing it does indeed
show you a bunch of sliders like the icon indicates.

Also add xhdpi and xxhdpi versions.

Change-Id: I944a325c8871e1afc9d7163b0f23f7f9d8ae070a