Add form modal and form settings

Modal implementation needs to be cleaned up for form settings.
Aren't you always passing in an ID, which will return a single element? In that case you can use `sel1` and don't need `doseq`, you can use `listen!` directly on the element, like here, https://github.com/onaio/zebra/blob/master/src/cljs/ona/project.cljs#L14. Unless I'm missing something?