Projection Operator configuration parameters change

["Pradeep A. Dalvi" <pr...@apache.org>]

Hi Folks,

Projection Operator accepts 2 config params: selectFields & dropFields.
Currently both these parameters accept values in comma-separated field
names format. However this is not inline with other operators do to accept
multiple values, for which they use List instead.

So this proposal is to make change in Projection Operator to accept config
params as List instead of comma-separated string. Hence selectFields &
dropFields shall accept List going forward.

Please feel free to let me know your thoughts on this.

Thanks,
Pradeep A. Dalvi