Styling for multi-units modal could use UX tuning

[ndebuhr]

The styling for the multiunits modal is a bit jarring. Could we move the Submit button to the lower right corner of the modal, and perhaps change the "Close" to cancel. Using standard UI/UX would suggest "Submit" in the lower left corner (same vertical positioning as the current "Close"), "Cancel" text in the bottom right button instead of Close, and an "x" button in the top right corner.