WIP: Add P2P Wireless support (Wi-Fi Direct)

This is a work in progress branch to add P2P Wireless (Wi-Fi Direct) support.

The current implementation is incomplete in a number of regards:

• Connection establishment requires connecting to a peer. The connection will be failed automatically if this peer disconnects (after 5 seconds).
• Proper WFD support will require setting a global wpa_supplicant property. This does not seem easily fixable. That could result in some weird from NM if one has multiple Wi-Fi cards.
• Information about the found P2P Groups is not available through NM
• The symbol versions (and documentation) is currently wrong

Other notes:

• The patchset creates a virtual P2PWireless device for every capable wireless device
• Meaning of IP auto-configuration can be modified by the device class. Something like this is needed for proper P2P support, but the solution may be bad.