Don't re-sort when adding filters

[richardlin047]

Currently, sorts are applied again after a filter is applied. As a performance enhancement, when a more restrictive filter is applied on the df, there is no need to re-sort. This may not be feasible if each additional filter is done on the unfiltered_df rather than the internal df.

We could refactor to apply filters onto the internal df, but this is a trade-off of inefficiency when replaying code and minimizing relevant history code vs. performance of widget.