Fix for GRILL-500 - Thrift union type support and HIVE-2390 - LazyBinarySerde support for UNION

Have added two TCs in ql/src/test/queries/clientpositive/input_lazyserde.q to test thrift deserializer changes and this also tests the 'LazyBinarySerDe' changes

Running all the related tests is still under progress. Please do not merge it until done.