0.6.0

• Fixes for list2list and basic list handling (still needs some improvement)
• Fix for ref cells when they have not yet been assigned
• Tests for list actions (still needs more)
• Question strands for lists work in a more reasonable way: corrected the code, updated docs, created tests for each type of Question Strand
• Added "reverse" commands to make it easier to work with lists
• Re-assigned the mod command
• Created Prime Tester sample program