Vectorization: IF Statements, Comparisons, and more do not handle NULLs correctly

 
Many vector expression classes are setting noNulls to true which does not work if the VRB is a scratch column being reused. The previous use may have set noNulls to false and the isNull array will have some rows marked as NULL. The result is wrong query results and sometimes NPEs (for BytesColumnVector).

So, many vector expressions need this:

      // Carefully handle NULLs...

      /*
       * For better performance on LONG/DOUBLE we don't want the conditional
       * statements inside the for loop.
       */
      outputColVector.noNulls = false;
 

And, vector expressions need to make sure the isNull array entry is set when outputColVector.noNulls is false.

And, all place that assign column value need to set noNulls to false when the value is NULL.

Almost all cases where noNulls is set to true are incorrect.