Some cosmetics + basic test coverage

- Move v3 module descriptions into V3ModuleDefinition
- Move hook declaration from Hook to \Bootstrap\Hooks\SetupAfterCache
- Extend ResourceLoaderBootstrapModule to allow to inject cache via setCache
- NS change from bootstrap to Bootstrap
- Adds SetupAfterCacheTest, ResourceLoaderBootstrapModuleTest,
BootstrapManagerTest, and V3ModuleDefinitionTest

Functionality is unaltered

Change-Id: I9c03a40a54db38f6d4191a9cec8f9f3c1a662920