Filtering Partial DataFrames in MultiIndex Column Thickets

[michaelmckinsey1]

If we have a MultiIndex Column Thicket with a performance table:

	A		B
	time	memory	time	memory
1	5s	10b	7s	6b
2	3s	8b	4s	9b

its profiles would be [(1, "A"), (2, "A"), (1, "B"), (2, "B")]. Currently, filtering applies to the profile and profile_mapping objects, but we do not filter the dataframe or metadata in this case unless the whole row would be removed (e.g. removing (1, "A") and (1, "B")). If we only remove (1, "A"), this will have no effect on the dataframe.

Should removing (1, "A") result in

	A		B
	time	memory	time	memory
1	NaN	NaN	7s	6b
2	3s	8b	4s	9b

?

If yes, then we need to develop functionality for this feature.