Rename SpringApplication Events

Move SpringApplication events to their own package, create a common
base class and rename classes to match Spring conventions.
Separate Application Listener and Initializer

Update SpringApplication so that ApplicationListener and
ApplicationInitializer methods must be called separately. This helps
to prevent unexpected side effects when calling the setters and
also encourages separation of concerns.

The few situations where a class was both an ApplicationInitializer
and ApplicationListener are now handled by registering an inner
listener from the `initialize` method.
Automatically detect 'development' profile

Detect when an application is running in development (by the presence
of a build file) and automatically add a 'development' profile.

Additional detectors can be developed by implementing the
`ProfileDetector` interface and registering with the `SpringApplication`

Fixes gh-296
Polish