Remove spacepen as a dependency (startup speed)

As the Atom team is currently removing Spacepen as a dependency in all their views, im also starting with rewriting it to use DOM API's. I will also update to the new configuration options.

**Tasks**
Remove spacepen
- [X] Rewrite statusbar view
- [ ] Extract table row in own view
- [ ] Rewrite PanelView

Other tasks
- [ ] Update configuration syntax (configDefaults)
- [ ] Fix CSS