Datagrid Styleable Column

[texodus]

Adds a column-style menu to each column header (only visible when the configuration panel is open). For now, configuration is only enabled for float and integer columns, and only fixed-precision and foreground/background/heatmap color are implemented. These new properties are fully persistent through the pre-existing plugin-config save/restore token key.

[texodus]

Streaming also.

In background and gradient modes, foreground is calculated automatically via first applying the translucent cell background to the viewer's --plugin--background, then calc perceived luminance, as ripped directly from Stack Overflow.