Add size_index to graphs

[ahuang11]

Try to address #3097, but I'm not really sure what I'm doing; just copying a bunch of code from the other scripts.

Still useless too because I can't seem to figure out where it only takes the first three(?) columns and converts it to ['index', 'x', 'y'](?) instead of ['index', 'x', 'y', 'test'] so size_index/color_index only works on either 'index', 'x' or 'y'... (I think if the three column restriction is removed, it'll help complement the fix to the image hover_col limit too(?) holoviz/geoviews#242 besides changing bounds=(1, None)))

[philippjfr]

I'd hold off on this, #2152 should already allow for this.

[ahuang11]

Okay. Still wondering where in the code are the columns changed to ['x', 'y', 'index']

[philippjfr]

That does sound like an issue, will have to look into it.

[philippjfr]

I'll close since I'll be addressing any issues that crop up in the ops PR.