Blender Git Loki

Spreadsheet Editor: Row filters

{F9930989 size=full}

This patch adds support for filtering out rows based on rules and values.
Filters will work for any attribute data source, they are a property of
the spreadsheet rather than of the attribute system.

**Further Questions**
* The popover is a test, it would be easy to move this to a sidebar, but I wanted to see
what people thought about the popover.
* `SpreadSheetColumn` does not know about the " X" suffixes that are added to vector columns.
This means the row filter cannot determine the correct data type for vector columns.
Luckily the default of float works, but I'm not sure how to handle this properly.

Differential Revision: https://developer.blender.org/D10959