Don't bother looking at the diff, this is almost a complete rewrite of
the previous Scala API. This uses all the work put into the Java API,
such as TypeInformation, the serializers and comparators and the
operators.

The Scala DataSet and ExecutionEnvironment wrap their respective Java
equivalents. TypeInformation is generated by a macro that uses
TypeInformationGen and other macro support classes. The Java
TypeExtractor is completely bypassed but the TypeInformation and
sub-classes are created by the Scala type analyzer. There is special
support for Scala Tuples in the form of ScalaTupleTypeInfo,
ScalaTupleSerializer, and ScalaTupleComparator.

This also adds tests to flink-scala that are ports of the tests in
flink-java.

There are not yet any Scala specific tests in flink-tests. All the
scala example ITCases are commented out, as well as the examples
themselves. Those will be uncommented once the examples are ported. This
will happen in separate commits.