Allowed parallel asynchronous calls

Resolves #1065

http://jenkins.buttonweavers.com:8080/job/buttonmen-AdmiralJota/255/

I updated many places to use this, but there may be some spots that I missed where we could usefully refactor to take advantage of parallel asynchronous calls (*possibly* including the spot where the Overview page loads prefs before performing monitor activities). We can address those individually as we discover them and decide how we want to handle them.

(Also, I put this in Env rather than Api under the theory that there could be some asynchronous calls other than API methods (like setTimeout, for instance). Is that fine, or would the Api namespace be preferred?)