Assign badge in modal

[LanesGood]

The current page approach for badges results in a number of potential concerns/bugs:

• I can visit the URL /organizations/:id/badges/assign/:userid with any values for :userid, even if the userid is not a part of the org, and no error is thrown. The page renders as expected and my only indication that something is wrong is if I try to assign the badge to a user who is not part of the org - then a toast is displayed
• I can visit the URL /organizations/:id/badges/assign/:userid with any values for :orgid, even if I am not a member of the org or if the org does not exist. No badges display, but no error is thrown until I try to assign a badge
• Now that #415 enables assigning badges from the team page, there is no easy way to click "assign badge" on the team and then navigate back to that team - the badge assignment page redirects to the org. While getting the location history from the router is possible, this seems like a more brittle solution

Assigning a badge in a modal would be a more straightforward way to approach this. The individual badge page at /organizations/:orgid/badges/:badgeid and badge-user-assignment page at /organizations/:orgid/badges/:badgeid/assign/:userid are both likely still necessary and useful; the badgeless assignment page at /organizations/:id/badges/assign/:userid is the one that seems most helpfully replaced by a modal.

Page refresh actions would be necessary, but this would seem to also help pave the way to team badges for teams which are not part of an organization.