Run against Isis 1.8.0-SNAPSHOT, disable custom application.css
Bumping up to use 1.8.0-SNAPSHOT of isis-wicket-* addons.
for ISIS-933: new RO viewer properties.
ISIS-537: added comments to properties in viewer_wicket.properties
tidy up of properties in isis.properties.
Bootstrap theme chooser, default theme.
Removed dependencies on defunct/mothballed modules (ISIS-936, ISIS-937, ISIS-938)

specifically:
* isis-core-objectstore-jdo-datanucleus removed, instead isis-core-runtime
* isis-core-objectstore removed, instead isis-core-runtime
Fixing the banner png and pdn.
Refactoring to work with singleton event bus (ISIS-948).

- register with event bus in @PostConstruct method, rather than inject
- replace some injectXxx() methods with @javax.inject.Inject instead
- override in subclass services that also call init, calling super.init(...) as required.
Updating fixtures to use executeChild(...) rather than the deprecated execute(...)