Improve the projection operator with renaming and re-ordering columns

We want to finish the PR #1134, which allows projection to re-order columns.

Ideally, the new projection operator can do: 1) re-order columns, 2) drop columns (by selecting the checkbox), and 3) rename columns.

But if it's hard to combine into one single operator, one alternative implementation is to have 1) a projection operator that can do reordering and dropping, and 2) add a new renaming operator that only does renaming.