Add support for expandable rows to EuiBasicTable.

[cjcenizal]

Fixes #466

[cjcenizal]

@elastic/kibana-design Could you spruce up the aesthetics of this feature after it's merged?

[snide]

Yep. Can do.

[walterra]

LGTM

[jgowdyelastic]

LGTM

[peteharverson]

LGTM.

[peteharverson]

I like the flexibility of using the itemIdToExpandedRowMap prop which provides flexibility in how the row expansion / contraction is triggered, with the example using Show / Hide links in a Details column. For the ML tables (Anomalies, Jobs List) we'd probably look to use arrow icons in the first column of the table - the tables can have a lot of columns so a 'Details' column as in the example here could get lost.

@elastic/kibana-design what are your thoughts on using the arrowDown / arrowRight EuiIcons to mirror the current behavior in the ML tables:

This would also require additional styling to shrink the width of the first table column holding the expand / contract icons. Is this something that could be built into the out-the-box eui styles, or should it be left it to the implementation?

[snide]

@peteharverson Looking at @cjcenizal's example it looks like we can make it whatever we want. Likely we'll set the default example up with a caret system with a minimized column. Generally when these are done I think it's smart to (optionally) make the whole row clickable. I'd certainly recommend that for your example considering there's no links in that example beyond the expanding mechanic. We shouldn't limit people to such a small hitbox in that case.

I can look into that as well when we get to styling it (soon after merge), but I think he's got the pieces we'd need.

Nice work.

[chrisronline]

LGTM!