[DAEMON-13] appcd: Fix source/user agent support
|Appc Daemon 1.0.0
For analytics, the daemon records the client's "user agent". This feature is currently implemented, but it's named "userAgent" which was determined to be misleading. We need a better term to describe this feature and a way to describe a client type, description, and version, possibly as a string instead of an object. NPM has a user agent string that looks like
npm/2.15.1 node/v4.4.3 darwin x64.