Allow User reordered filter pins

[combinatorist]

It seems no matter how times I unpin or delete a filter on a widget, it will always reappear in the same order relative to the other filters. In terms of filtering logic, it makes sense that order doesn't matter.*

However, there are times order of the pinned filters is very import to a visual logic. For example, almost all my grist documents have some parent/child or dependency relationship between records of a single table. Because I'm essentially trying to visualize and navigate a graph of relations it help to place widgets left to right along that transitive relation of dependency, even on different pages, showing different things. So, if I pin filters to a widget in the middle, it helps to have the pinned filter on blockers be on the left so it appears toward the other widgets that list blockers, etc.

*It seems it currently orders them based on column creation time, so I suppose I could create a new view column as a workaround, but of course that's not very elegant. It also might be tempting for users to rename columns in case they'll alphabetize, but that doesn't work according to my testing.