Fugue support for extra helper functions from core

[fdosani]

Currently there are some helper functions as part of the core Pandas code which I think are generally very helpful.
We need to spend some time exploring those and seeing which ones can be mirrored/included via the Fugue implementation.

This is just a list of most of the functions. Not all will make sense to move over. But we should investigate which ones make sense to:

• df1_unq_columns (adding in unq_columns and intersect_columns for Fugue #217)
• df2_unq_columns (adding in unq_columns and intersect_columns for Fugue #217)
• intersect_columns (adding in unq_columns and intersect_columns for Fugue #217)
• all_columns_match (adding in all_columns_match #219)
• all_rows_overlap (adding all_rows_overlap to fugue #244)
• count_matching_rows (Fugue count matching rows #294)
• intersect_rows_match
• matches (is_match)
• subset
• sample_mismatch
• all_mismatch
• columns_equal
• compare_string_and_date_columns

Need to look into a bit more. low prio for now.

• get_merged_columns
• temp_column_name
• calculate_max_diff
• generate_id_within_group

[fdosani]

@goodwanghan @kvnkho FYI, no pressure to contribute, but something in our backlog I'm thinking to ensure full parity in terms of function etc.

[goodwanghan]

Sounds good, let's chat about it