Remove javacard.framework public constructors
Remove AID#toString()

- Remove AID#toString() so that it does not show in javadoc
- Add AIDUtil#toString method
Add test case: APDU without selected applet fails
Code cleanup

- Use generics for Class and collections
- Remove redundant imports
- Remove redundant casts
Improve memory handling in HelloWorldApplet

- Only allocate memory in constructor
- Re-use transient memory buffer
Remove transient memory leaks

Remove unnecessary JCSystem.makeTransientByteArray calls
Remove outdated null-checks
Merge pull request #52 from robertbachmann/code_cleanup

Code cleanup