Responding to pull request review feedback

- messages.getQuoteObjectUrl: early return
- backup.js: explaining variables for long if statement
- types/messages.js: Log if thumbnail has neither data nor path
- sendmessage.js:
  - remove extraneous logging
  - fix indentation
  - upload attachments and thumbnails in parallel
- preload: don't load fs for tests, just fse
- _conversation.scss: split two selectors into two lines, 0px -> 0
- backup_test.js: use fse.existsSync and comment twoSlashes regex
- network_tests_view_test.js: Comment duplicate assignment to window.getSocketStatus

test/views/network_status_view_test.js

@@ -14,6 +14,11 @@ describe('NetworkStatusView', function() {
 
         after(function() {
             window.getSocketStatus = oldGetSocketStatus;
+
+            // It turns out that continued calls to window.getSocketStatus happen
+            //   because we host NetworkStatusView in three mock interfaces, and the view
+            //   checks every N seconds. That results in infinite errors unless there is
+            //   something to call.
             window.getSocketStatus = function() { return WebSocket.OPEN; };
         });
         /* END stubbing globals */