Adding a simple message after the build if JDK is < 7.

Haven't found a better way to do this. So right now just a message at the end:
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* Warning:
JDK 1.7 is minimal requirement for building the driver. You have 1.6.
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Added DBAddress class to driver-compat
Changed return type of BSON.decode to BSONObject, for binary compatibility.
Fixed several bugs in JSON reader and writer in relation to values with binary subtype > 127, which turn into a byte with a negative value.
Added support for multiple decoded types for binary values, depending on subtype.  Required the introduction of a new interface, BinaryTransformer.  Refactored Binary and UUID codecs to fit into the new framework
Merge branch '3.0.x' into merge-test
Added field level validation for POJOs that will not allow "$" at the start of a variable name.  This is to stop the Jacoco instrumentation failing the tests, but is also probably a Good Thing anyway