Hive UDFs
1. Generate code for using GenericUDF
2. Add new expression FunctionHolderExpression
3. In materialization convert FunctionCall into FunctionHolderExpression
4. Support for TINYINT, SMALLINT, INT, BIGINT, FLOAT4/8, VARCHAR and BIT in ObjectInspectorHelper
5. Add test cases to test few more UDFs (SimpleUDF.json)