Build with Java 7 when using Maven.

I see that Java 7 support was added in Android build tools 19, and we
need this for things like the diamond operator which was used in a
recent commit (and I'm assuming compiled in Eclipse).
Replace tabs with 4 spaces.
Add a more specific toString to NamedVehicleMessage.
Test equals overridden on NamedVehicleMessage.
Test r/w a NamedVehicleMessage to a Parcel.
Update JSON deserialization tests.

One of these no longer applies as the deserializer doesn't check which
fields are there, just that it is valid JSON.
Whitespace.
Run openxc library tests separately from integration tests in CI.