FIX: invite to message was not allowing groups

Previously we were incorrectly checking mentionable instead of messageable

Also fix edge case where multiple groups sharing a name mean that exact match override is not working

Also cleans up params sent to user selector

test/javascripts/lib/user-search-test.js.es6

@@ -47,6 +47,10 @@ QUnit.module("lib:user-search", {
             }
           ],
           groups: [
+            {
+              "name": "bob",
+              "usernames": []
+            },
             {
               "name": "team",
               "usernames": []
@@ -61,4 +65,4 @@ QUnit.test("it places groups unconditionally for exact match", assert => {
   return userSearch({term: 'Team'}).then((results)=>{
      assert.equal(results[results.length-1]["name"], "team");
   });
-});
+});