ISIS-728, ISIS-729: config-based audit and commands

In detail:
- @Command and @Audited now have disabled flag
- new CommandFromConfigurationFacetFactory and CommandFacetFromConfiguration
- new AuditableFromConfigurationFacetFactory and AuditableFacetFromConfiguration
- in ActionInvocationFacetViaMethod, check that command is not disabled
- in IsisTransaction, check that auditable facet is not disabled

Also:
- renamed existing facet factory and facet for @Auditable annotation, added unit test
- added pngs for audit entry, command, published event
- new JDOQL queries for commands, available in CommandServiceJdoRepository#findByFromAndTo
- new JDOQL queries for audit entries available in AuditingServiceJdoRepository#findByFromAndTo
- new JDOQL queries for published events, available in PublishingServiceJdoRepository#findByFromAndTo
- recentChanges contributed action now includes published events
- listAll() removed from BackgroundCommandServiceJdoRepository
- updates to todo app to expose new JDOQL queries in Admin menu
- updated some icons in example todo app