Removed the annoying opening image

It is useless since it is not a real splah screen that opens before the
beginning of the program... One should use the real java splash screen.
Replaced the "javax.swing." with imports
Minor refactoring of FizzimGUI.java

- Remaned JTabbedPane1 into pages_tabbedPane.
- Move the declaration of the private variables to the beginning of the class
Turned the dependency of FizzimGUI on swing-layout to the Java 1.7 GroupLayout
Dependency on lib/swing-layout-1.0.3.jar removed