Devices app: Update interfaces, fix threads, add configs

This CL tackles a few small issues with the devices app:

 * Interface field names are updated to be more
   consistent with WebUSB names.
 * The DeviceManager impl no longer uses UsbDevice
   objects from the wrong (i.e. non-UsbService) thread.
 * DeviceInfos are now populated with all device configs
   rather than only the active config.

Additionally the devices app URL is changed to mojo:devices
to be consistent with other Mojo apps.

BUG=None
[email protected]

Review URL: https://codereview.chromium.org/1291643003

Cr-Commit-Position: refs/heads/master@{#343125}
8 files changed