Refactored launcher initialization into its own task.
- introduced new `LauncherConfiguration` which collects the information needed for creating the main launcher frame.
- the `LauncherConfiguration` is assembled by a new task `LauncherInitTask`
- the progress of the init task is observed by a (dummy) splash screen.
Removed old Swing classes.
Updated the splash screen.
- splash screen with progress bar and message field
- new splash image, css style for splash screen
- updated BundleUtils to javafx.Image
Merge pull request #268 from skaldarnar/javafx

More JavaFX work