Updated for new authentication protobuf

Changed console output that reads a receive Authentication protobuf

Change-Id: Idd12f79e508da0e998be5b9f3d88af554c61ddae
Session handling update

Depends on matching commit for svmp-protocol-def.
Added support for issuing and handling sessions/session tokens.
Added support for timing out a running session and sending a message to
re-authenticate.

Change-Id: I02dd0ee0a4043744c0f91c2c70fa809f41de7d6c
Session handling update 2

Added support for idle session timeouts

Change-Id: Ia84552750f053dc0c499f1d55a49270cff544d6c
Session handling update 3

Removed AuthenticationEntry and Authentication protobufs, added
AuthRequest and AuthResponse protobufs with optional fields for
sending and receiving auth data. JSON is no longer used in the
Response "message" field for sending auth response data.

Change-Id: Ia1b3001cb4c8a357d5f15943292d88fc089698d5
Add gradle build system
Clean up and simplify ant/gradle builds and README

Automatically uses protobuf jar and SVMPProtocol.java from the
svmp-protocol-def project that is assumed to be checked out in a
directory parallel to the test-proxy.

Gradle now uses svmp-protocol-def as as subproject and doesn't need
any file copying tricks or ant custom rules to generate code straight
from the .proto definition file.

Change-Id: I605d932587ff0aee09f5961853f3d55d89827813
Fix README markdown rendering
Fix README markdown rendering again