[$30] - New Listing - clean up constants

[ajefts]

I've noticed quite a few cases of using hardcoded constants for things like api urls. These need to all be part of config and able to be different for dev/qa/prod environments.

For example, right now, a search of the /components folder in react-components returns about 20 results. All of these should be determined dynamically, using props like MAIN_URL.

[ajefts]

@tladendo This might be good for a short cleanup code challenge. Let's do it soon as I know want it to propagate for too long...

[tladendo]

@tonyJ how about launching another bug bash for cleanup? that way i can just make tasks for all the little outstanding things while also cleaning up other remaining issues