Refactoring and Testing JumbleSort

Quite a lot of changes to the JumbleSort system. Refactored JumbleSort
to use a RandomStrategy and a SortedCriteria respectively. These help
testing and improve flexibility.
Added AllTests for easier testing.
Implementing JumbleSort null handling

Implementing null handling on JumbleSort. At the minute a null pointer
exception is thrown.
Added null handling and checked object sorting

Implemented null-object handling. JumbleSort now puts all null objects
last in the list.
Tested that complex objects with fields are correctly sorted.