Factored browser code into new component, eschewing the procedural style being used before
Login event
Moved event registration into browser component
Hid correct header on mobile
Fixed login logic; exposed current issue to IssueCommentsDisplay on clicking details button
Made use of single-thread executor instead of raw threads; pages also won't reload if the target issue is already displayed
Doc comments and cleanup
Fixed NPE when quitting before logging in
Browser exits on quitting application
Eliminated EventBus errors; reasons and method are documented in EventHandler