* Serve translation files from the karma server
* Port UserSettingsStore to ES6 exports because the test runner
gets confused by ES6 importing a commonjs module
* Remove extra spaces in translations strings for MELS
* Fix 'his/her' back to be 'their'
* Change test to expect singular 'invitation' for a single person
(there may be multiple invitations, but IMO this should be
'rejected n invitations' and we can play with the wording later,
I don't think the singular is any worse than the plural).
* set language in the MELS tests (and wait for it to complete)
* Don't bother setting lang in other tests for now
Don't include src in resolve root for the karma test, as otherwise
modules from react sdk get pulled in instead of npm libraries like
'extend' which breaks everything in really subtle ways.
By adding a way to wait a short time for a component to appear in
the DOM, so we don't get flakey failures like this when we change
something to returning a promise that needs to resolve before the
component actually appears.