Add search/multiselect component to coreui

[asizemore]

For the network apps, we're hoping to add a searchable multiselect, basically like the "Multi" version of react-select.

We could use the above multi-select, but it's pretty different to our current styles. Also we'd want checkboxes (id imagine) because that's how all of our other multi-selects work.

Thoughts? Open for comments :)

Note we can add checkboxes with react-select using the components option