Offer to detect non-SSL/TLS network traffic.

Introduces new module that provides network-related features for
the StrictMode developer API.  The first feature offers to detect
sockets sending data not wrapped inside a layer of SSL/TLS
encryption.

When a developer enables, we ask netd to watch all outgoing traffic
from our UID, and penalize us accordingly if cleartext sockets are
detected.  When enabled, netd captures the offending packet and
passes it back to the owning process to aid investigations.  When
death penalty is requested, all future traffic on the socket is
blocked, which usually results in a useful stacktrace before the
app is actually killed.

Bug: 18335678
Change-Id: I3adbc974efd8d3766b4b1a23257563bb82d53c29