Refactor setting the tableView backgroundColor in LoginController

Setting the 'tableView.backgroundColor' before `viewWillLoad:` will not work. This is because the background colour is now being set by either 'root.appearance.tableViewBackgroundColor' or 'root.appearance.tableGroupedBackgroundColor'.

- Updated the root element's appearance when the tableView is set.
- Changed the colour to better match the section header
Merge branch 'bugfix/QDTableViewBackgroundColor'

Conflicts:
	sample/LoginController.m