Initial setup of filterbox on popover.

[derivagral]

Did PairFilterBox pretty quick, open to refactors.

Styling's very basic; good-enough?

[freeatnet]

I think we're on the right track UI-wise. I've thrown a bit of styling overtop the component, seen above. Does it look right to you?

Styling as seen:

1. Add .pt-input to the search field. Override .pt-input[type="search"] border-radius to use default for input components.
2. Wrap that in a .pt-input-group .pt-large (see: http://blueprintjs.com/docs/v1/#core/components/forms/input.search-field)
3. Wrap that in a <div> with style padding: 6px 8px; box-shadow: inset 0 0 0 1px rgba(16, 22, 26, 0.2), 0 0 0 rgba(16, 22, 26, 0), 0 1px 1px rgba(16, 22, 26, 0.4);

[derivagral]

I can move the filterstate into redux, sure. Initially I wasn't sure that it'd need the wider scope, but being able to share the filter/selection from the popover box to any other select dialog would be kind of nice. I should get some time for that tomorrow afternoon.